Symposium on
Quantum
Materials
Synthesis:
Grand Challanges and Opportunities
August 30 - September 1, 2016
7 World Trade Center | New York, NY
Plenary Speaker
Shuji Nakamura, Professor
University of California, Santa Barbara
Nobel Prize in Physics, 2014
Shuji Nakamura was born on May 22, 1954 in Ehime,
Japan. He obtained B.E., M.S., and Ph.D. degrees in
Electrical Engineering from the University of Tokushima,
Japan in 1977, 1979, and 1994, respectively. He joined
Nichia Chemical Industries Ltd in 1979. In 1988, he spent
a year at the University of Florida as a visiting research
associate.
In 1989 he started the research of blue LEDs using groupIII nitride materials. In 1990, he developed a novel MOCVD
system for GaN growth, which was named Two-Flow
MOCVD. Using this system, he could grow the highest
crystal quality GaN-based materials. From his perspective, the invention of Two-Flow MOCVD
was the biggest breakthrough in his life and his GaN-based research.
In 1991, he obtained p-type GaN films by thermal annealing for the first time and finally he
could clarify the Hydrogen passivation as a hole compensation mechanism for the first time.
This hydrogen passivation of the acceptors had hindered to obtain p-type GaN films since
the beginning of GaN research in 1960s done by many researchers.
In 1992, he also could grow the first InGaN single crystal layers which showed the first band
to band emission in PL and EL at room temperature. These InGaN layers have been used
for an emitting layer of all of the blue/green/white LEDs and all of the violet/blue/green
semiconductor lasers. Without his invention of InGaN layers, there have been no blue/green/
white LEDs and no violet/blue/green semiconductor laser diodes.
In 1993 and 1995 he developed the first group-III nitride-based high-brightness blue/green
LEDs. He also developed the first group-III nitride-based violet laser diodes (LDs) in 1995. In
1996, his former company, Nichia, started selling white LEDs using his invention of blue LEDs.
These white LEDs have been used for all kinds of lighting applications in order to save energy
consumptions. The electric consumption of white LEDs is about one tenth in comparison
with that of conventional incandescent bulb lamp nowadays. In 1999, Nichia started selling
the violet laser diodes for the application of blue-ray DVDs. Without his invention of violet
laser diodes, the blue ray DVD was not realized.
Professor Nakamura had received numerous awards for his work, including the Nishina
Memorial Award (1996), the Materials Research Society Medal Award (1997), the Institute
of Electrical and Electronics Engineers Jack A. Morton Award, the British Rank Prize (1998),
the Benjamin Franklin Medal Award (2002), the Millennium Technology Prize (2006), the
Czochralski Award (2007), the Prince of Asturias Award for Technical Scientific Research
(2008), The Harvey Award (2009), and the Technology & Engineering Emmy Award (2012)
awarded by The National Academy of Television Arts & Sciences (NATAS). He was elected as a
fellow of the U.S. National Academy of Engineering in 2003. He is the 2014 Nobel Laureate in
Physics for the invention of efficient blue light-emitting diodes which has enabled bright and
energy-saving white light sources. Prof. Nakamura received the 2014 Order of Culture Award
in Japan. He was inducted into the National Inventors Hall of Fame in 2015. He received the
2015 Charles Stark Draper Prize for Engineering and the 2015 Global Energy Prize in Russia.
Since 2000, he has been a professor of Materials and Electrical & Computer Engineering at
the University of California, Santa Barbara. He holds more than 200 US patents and over
300 Japanese patents. He has published over 550 papers in his field. Prof. Nakamura is the
Research Director of the Solid State Lighting & Energy Electronics Center and The Cree
Chair in Solid State Lighting & Displays. He co-founded Soraa, Inc. in 2008, which operates
vertically integrated fabrication facilities in California’s Silicon Valley and Santa Barbara.
http://ssleec.ucsb.edu/nakamura
Sponsors
Rutgers School of Arts and Sciences (SAS)
Rutgers University School of Engineering (SOE)
Department of Physics and Astronomy
The Institute for Advanced Materials, Devices and Nanotechnology (IAMDN)
ORGANIZING COMMITTEE
Sang Wook Cheong ([email protected])
Seongshik Oh ([email protected])
Jak Chakhalian ([email protected])
August 30, 2016
Agenda - DAY ONE
8:00am
REGISTRATION / NETWORKING
8:45am
OPENING REMARKS
Sang Wook Cheong, Rutgers University, Department of Physics and Astronomy
Seongshik Oh, Rutgers University, Department of Physics and Astronomy
Jak Chakhalian, Rutgers University, Department of Physics and Astronomy
9:00am
PLENARY TALK: Invention of blue LED and future lighting
Shuji Nakamura, University of California, Santa Barbara
SESSION 1: ENERGY MATERIALS
Chair: Martha Greenblatt, Rutgers University, Department of Chemistry/Chemical Biology
9:40am
Interfacial management of hybrid perovskite solar cells toward high
performance and stability
Tsutomu Miyasaka, Toin University of Yokohama
10:10am Semiconductor nanowires for energy conversion
Peidong Yang, University of California, Berkeley
10:40am
BREAK
SESSION 2: DISSIPATIONLESS CONDUCTORS SUPERCONDUCTIVITY
Chair: Stuart Parkin, Max Planck Institute of Microstructure Physics
11:10am Why is Tc in cuprates so high?
Ivan Bozovic, Brookhaven National Laboratory
11:40am High temperature conventional superconductivity
Mikhail Eremets, Max Planck Institute for Chemistry
12:10pm Topology, magnetism and high-spin superconductivity in
half-Heusler semimetals
Johnpierre Paglione, University of Maryland
12:40am
LUNCH
SESSION 3: DISSIPATIONLESS CONDUCTORS SUPERCONDUCTIVITY/QUANTUM (ANOMALOUS)
HALL EFFECT
Chair: David Vanderbilt, Rutgers University, Department of Physics and Astronomy
1:40pmHigh-Tc superconductivity in FeSe electric-double-layer transistor
Atsushi Tsukazaki, Institute for Materials Research, Tohoku University
2:10pm
Searching for materials that show the quantum anomalous Hall effect
at higher temperature
Ke He, Tsinghua University
2:40pm
Quantum anomalous Hall state and dissipationless chiral conduction
in topological insulator thin films with broken time reversal symmetry
Jagadeesh Moodera, Massachusetts Institute of Technology
3:10pm
Bulk-insulating topological insulators and spin-helical Dirac fermion
topological surface transport
Yong Chen, Purdue University
3:40pm
BREAK
SESSION 4: DISCUSSION -- MATERIALS FOR ROOMTEMPERATURE DISSIPATIONLESS CONDUCTORS
Chair: Jak Chakhalian, Rutgers University, Department of Physics and Astronomy
Chair: Qi-Kun Xue, Tsinghua University
4:10pm
Interface engineering of high temperature superconductivity
Qi-Kun Xue, Tsinghua University
4:20pm
Designer materials for topological pahses with strongly correlated electrons
Jak Chakhalian, Rutgers University, Department of Physics and Astronomy
4:30pm
DISCUSSION
5:30pm
POSTER SESSION
6:30pm
BANQUET (until 9:00pm)
Post-Dinner Talk
Sang Wook Cheong, Rutgers University, Department of Physics and Astronomy
Wi-Fi Log-in/Password: QMS2016
Agenda - DAY TWO
August 31, 2016
SESSION 5: 2D MATERIALS
Chair: Charles Ahn, Yale University
8:00am
AMX2 layered materials (M= transition metal; X= O, S, Se):
From thermoelectrics to multiferroics through 2D metals
Antoine Maignan, Laboratoire CRISMAT CNRS/ENSICAEN/UCBN
8:30am
Phase transition engineering of 2D layered materials
Young-Hee Lee, Sungkyunkwan University
9:00am
Phase engineered transition metal dichalcogenides for
enegrgy and electrons
Manish Chhowalla, Rutgers University, School of Engineering (SOE)
9:30am
Creating heterointerfaces with textured electronic states on
correlated transition metal dichalcogenides
Han Woong Yeom, Institute for Basic Science and POSTECH, Pohang University
10:00am
BREAK
SESSION 6: NEW MATERIALS
Chair: Jan Musfeldt, University Of Tennessee
10:30am Novel transition-metal oxides with unusual valence cations
Yuichi Shimakawa, Kyoto University
11:00am Design of advanced materials?
Matthew Rosseinsky, University of Liverpool
11:30pm High pressure zone growth of correlated electron oxides
John Mitchell, Argonne National Laboratory
12:00pm Isotopically enriched materials for quantum computing
Jason Petta, Princeton University
12:30am
LUNCH | POSTER SESSION
SESSION 7: TOPOLOGICAL MATERIALS
Chair: Bob Cava, Princeton University
2:00pm
Heusler compounds: tunable materials with non-trivial topologies
Claudia Felser, Max Planck Institute for Chemical Physics of Solids
2:30pm
Nearly degenerate ordered states in frustrated quantum magnets
James Analytis, University of California, Berkeley
3:00pm
Electronic materials with frustrated lattices
Joseph Chechelsky, Massachusetts Institute of Technology
3:30pm
BREAK
SESSION 8: PROBES I
Chair: David Mandrus, University of Tennessee
4:00pm
Electronic Microscopy: a spacial probe for nano-scale materials excitations
Phil Batson, Rutgers University, Institute for Advanced Materials, Devices
and Nanotechnology (IAMDN)
4:30pm
Collective modes of electron-hole condensate in the (putative) excitonic
insilator, TiSe2
Peter Abbamonte, University of Illinois
5:00pm
Shining light on topological insulators
Nuh Gedik, Massachusetts Institute of Technology
5:30pm
DINNER ON YOUR OWN
SESSION 9: DISCUSSION -- TOPOLOGICAL
AND OTHER CLEAVABLE QUANTUM MATERIALS BOTTLENECKS AND PROSPECTS
Chair: Yi Cui, Stanford University
Chair: Seongshik Oh, Rutgers University, Department of Physics and Astronomy
8:00pm
Synthesis and property tuning of 2D layered materials
Yi Cui, Stanford University
8:10pm
Materials issues in topological materials
Seongshik Oh, Rutgers University, Department of Physics and Astronomy
8:20pm
DISCUSSION (until 9:30pm)
Agenda - DAY THREE
September 1, 2016
SESSION 10: OXIDE ENGINEERING I
Chair: Ho Nyung Lee, Oak Ridge National Laboratory
8:00am
Complex oxides in the 2D li
Harold Hwang, Stanford University
8:30am
Observation of polar vortices in oxide superlattices
Ramamoorthy Ramesh, University of California, Berkeley
9:00am
Expanding phase diagram of BaBiO3 via controlling thickness and doping
Tae Won Noh, Institute for Basic Science, Seoul National University
9:30am
Control of interfacial octahedral rotations in oxide heterostructures
Gertjan Koster, University of Twente
10:00am
BREAK
SESSION 11: PROBES II
Chair: Chang-Beom Eom, University of Wisconsin - Madison
10:30am Direct time-domain observation of attosecond electron dynamics in
occupied bands in solids
Margaret Murname, Joint Institute for Lab Astrophysics,
University Of Colorado, Boulder
11:00am Non-equilbrium phases of nickelate heterostructures:
From visualizing synthesis to driven dynamics
John Freeland, Argonne National Laboratory
11:30pm New physics emerged from old materials
Hong Ding, Institute of Physics, Chinese Academy of Sciences
12:00pm Big, deep, and smart data in atomically resolved imaging:
A bridge to accelerating materials by design
Sergei Kalinin, The Institute for Functional Imaging of Materials
12:30am
LUNCH | POSTER SESSION
SESSION 12: OXIDE ENGINEERING II
Chair: Andy Millis, Columbia University
2:00pm
Tuning the band structure of ruthernates with strain and dimensionality
Darrel Schlom, Cornell University
2:30pmFe3O4 thin films: controlling and manipulating and elusive
quantum material
Liu Hao Tjeng, Max-Planck Institute for Chemical Physics of Solids
3:00pm
Manipulating electronic phase separation in complex oxides
Jian Shen, Fudan University
3:30pm
BREAK
SESSION 13: DISCUSSION -- CHARGED INTERFACES THE MECHANISM OF CHARGE COMPENSATION
Chair: Jochen Mannhart, Max-Planck Institute For Solid State Research
Chair: Sang Wook Cheong, Department of Physics and Astronomy, Rutgers University
4:00pm
Novel quantum-matter heterostructures
Jochen Mannhart, Max-Planck Institute for Solid State Research
4:10pm
Charge compensation at polar or ferroelectric interfaces
Sang Wook Cheong, Department of Physics and Astronomy, Rutgers University
4:20pm
DISCUSSION
5:30pm
CLOSING REMARKS (until 6:00pm)
Future of the QMS Symposium
Sang Wook Cheong, Department of Physics and Astronomy, Rutgers University
Seongshik Oh, Department of Physics and Astronomy, Rutgers University
Jak Chakhalian, Department of Physics and Astronomy, Rutgers University
Presentations
Peter Abbamonte, Ph.D, Condensed Matter Physics, University of Illinois
Collective modes of the electron-hole condensate in the (putative) excitonic insulator, TiSe2.
An excitonic insulator is an instability of a dilute semimetal involving spontaneous proliferation
of excitons in the ground state at low temperature. This phase was predicted in the 1960’s, but
has never been definitively observed experimentally. The problem is that nearly all the physical
observables of an excitonic insulator, such as the opening of a gap and the appearance of a
structural superlattice, are the same as those of a conventional Peierls charge density wave (CDW),
making it challenging to distinguish these two types of phases.
Here, we use meV-resolved, momentum-resolved electron energy-loss spectroscopy (M-EELS) to
study the dispersion of the low-energy plasmon excitations in the zero-gap semimetal, 1T-TiSe2. We
found, at T = TC = 200 K, that the 35 meV plasmon disperses to zero frequency at the wave vector of
the superlattice, indicating the soft mode of the phase transition is electronic, rather than structural,
in origin. This excitation hardens at T << Tc into a nondispersive, gapped excitation at 50 meV that
can be interpreted as an amplitude mode of the electron-hole condensate. Our study is the first
observation of a soft plasmon in condensed matter physics and the first definitive evidence for an
excitonic insulator phase in a real material.
James Analytis, Department of Physics, University of California, Berkeley
Nearly degenerate ordered states in frustrated quantum magnets.
Recent advances in the synthesis and characterization of exotic materials have revealed new classes
of emergent phenomena in correlated electron systems. Here I discuss a recent study of Mott-Kitaev
honeycomb iridates, frustrated quantum magnets that are thought to be proximal to an exotic state
of matter known as a Kitaev quantum spin liquid. In theory, small imbalances in the interactions of
these systems allow a number of possible magnetically order states. We show that the application
of small magnetic fields can tune the systems between different ordered states but without ever
causing a true phase transition, a signature of the intrinsic frustration of the system.
P.E. Batson, Rutgers University, Institute for Advanced Materials Devices and Nanotechnology (IAMDN),
Department of Physics and Astronomy, Department of Materials Science and Engineering
Electron Microscopy: A Spatial Probe for Nano-Scale Materials Excitations.
Electron Microscopy has a long history of the detailed use of elastic and inelastic electron scattering
to reveal atomic structure, composition and functionality of materials. This has become more
and more important as nanoscale structures are increasingly engineered at the atomic level to
explore emergent properties that depend on the interaction of normally independent materials
quantities: magnetic, dielectric, optical, electronic, thermal and structural. During the past two
decades, aberration correction instrumentation has revolutionized performance, now routinely
producing sub-Angstrom spatial resolution,[1] and more recently pushing inelastic scattering
energy resolution to the 10 meV level, using a 1-1.2Å electron probe with a beam current of a few
pico-amps at 60 KeV.[2] This instrumentation has begun to yield spatially resolved measurements
of nanoscale structures: bulk phonon spectra down to 40 meV in energy; surface phonon polariton
behavior – Fuchs-Kliewer modes – in a polar oxide[3], surface polariton modes in a topological
insulator – Dyakonov modes,[4] in addition to a multitude of plasmonic and photonic excitations in
the 100-2000 meV range that have not been explored in the past with spatial resolution, including
acoustic plasmons, carrier plasmons, and band edge excitons. The polariton, “Aloof” scattering
in the microscopy community, is very long ranged, producing spectral results that are very
similar to IR absorption. But, in addition, bulk modes, which drive the polariton behavior through
“Begrenzen” boundary coupling, are also accessible.[3] Finally, a fundamental materials quantity,
the spatial- and time-dependent excitation correlation function will soon be become easily
available through numerical evaluation of spatially resolved inelastic scattering, expanding upon
similar measurements using inelastic x-ray and electron scattering.[5,6] Thus, new measurement
capabilities are resulting in qualitatively new and exciting information about the nanoscale behavior
of materials. I gratefully acknowledge financial support through Rutgers IAMDN, and the U.S.
Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0005132.
References: [1] P.E. Batson, N. Dellby, and O.L. Krivanek, Nature, 418 617-620 (2002). [2] O.L.
Krivanek, et al. Nature, 514 209-212 (2014). [3] M.J. Lagos, A. Trugler, U. Hohenester, and P.E. Batson,
in preparation. [4] N. Talebi, et al. ACS Nano, (2016). 10.1021/acsnano.6b02968 [5] P. Abbamonte, et
al. PRL 92 237401 (2013). [6] M. Bosman, et al. Scientific Reports 3 1312 (2013). 10.1038/srep01312
Ivan Božović, Brookhaven National Laboratory; Yale University
Why is Tc in cuprates so high?
Superconductivity in cuprates has many mysterious facets, but the central question is why the
critical temperature (Tc ) is so high. Our experiments target this question.
We use atomic-layer-by-layer molecular beam epitaxy to synthesize atomically perfect thin films
and multilayers of cuprates and other complex oxides. By atomic-layer engineering, we optimize
the samples for the particular experiment. Using a continuous spread in composition we tune the
doping level in steps of 0.01%. We use high-throughput measurements on combinatorial libraries to
study magneto-resistance and Hall effect in fields up to 90 T and measure accurately the coherence
length ε. We measure the absolute value of penetration depth λ to accuracy better than 1%.
We have shown that HTS films can be quite homogeneous, having a very uniform SC gap. Charge
density waves and charge glass are observed in underdoped LSCO samples, but none at optimal
doping. Phase fluctuations are seen up to 10-15 K above Tc, so the pseudogap must have a different
origin. In-plane charge excitations are strongly coupled to out-of-plane lattice vibrations. Superfluid
can be confined to a single CuO2 layer, with Tc equal to that in bulk samples. A large enhancement
of Tc is seen in certain heterostructures. Pairs exist on both sides of the superconducting transition,
be it induced thermally or by doping. [1]
I will present the results of a comprehensive study that took ten years and thousands of cuprate
samples, perhaps without precedence in Condensed Matter Physics. The large statistics reveals
clear trends and intrinsic properties; this is essential when dealing with complex materials such as
cuprates. We have measured the key physical parameters (Tc, λ and ε) of the superconducting state
and established their precise dependence on doping, temperature, and external fields. The findings
bring in some great surprises, challenge the commonly held beliefs, rule out many models, and
answer our initial question.
References: [1] Nature 534 (2016), 472, 458 (2011); 455, 782 (2008); 422, 873 (2003); Science 326,
699 (2009); 316, 425 (2007); 297, 581 (2002); Nature Materials 12, 877 (2013); 12, 387 (2013); 12,
1019 (2013); 12, 47 (2013); 11, 850 (2012); Nature Physics 10, 256 (2014); 7, 298 (2011); Nature
Nanotechnology 9, 443 (2014); 5, 516 (2010); Nature Communications 2, 272 (2011); Phys. Rev.
Letters 106, 237003 (2011); 102, 107004 (2009); 101, 247004 (2008); 93, 157002 (2004); 89, 107001
(2002); Proc. Nat. Acad. Sci. 113 (2016), 107, 8103 (2010).
Jak Chakhalian, Rutgers University, Department of Physics and Astronomy
Designer materials for topological phases with strongly correlated electrons.
Deterministic control over the periodic geometrical arrangement of constituent atoms is the
backbone of the material properties, which along with interactions defines the electronic and
magnetic ground state. Following this idea, a bilayer (2 unit cells) of a compound with perovskite
structure layered along the pseudocubic [111] direction yields a novel flexible method to design
a honeycomb lattice with almost arbitrary choice of ions. Here we discuss synthesis challenges for
layered complex oxide materials grown in 111 direction illustrated with artificial rare-earth orthonickelates. This important lattice geometry lays the foundation for a novel class of 2D topological
materials based on strong electronic interactions.
Presentations
(CONTINUED)
Joe Checkelsky, Department of Physics, Massachusetts Institute of Technology
Electronic Materials with Frustrated Lattices.
Geometrically frustrated lattices give rise to electronic correlation that results in complex magnetic
orderings, quantum spin liquid ground states, and other emergent phases. While such systems
are typically electronic insulators constructed from low connectivity lattices, recently a variety of
frustration-related effects have been explored in systems that have itinerant electrons. Examples
include lattice model realizations of the fractional quantum Hall effect and superconductors with
exotic pairing symmetries. Here I will present our experiments using itinerant electrons to probe
the behavior of kagome, triangular, and related frustrated lattice systems. Electronic transport is
found to be a complementary probe to magnetic and scattering experiments. The Hall effect in
particular acts as an incisive diagnostic for complex magnetic orderings. The further introduction
of strong spin-orbit coupling offers a new perspective in to correlated topological phases. I will
discuss the prospects for future experiments that build on these findings to realize model frustrated
systems.
Yong P. Chen, Purdue University
Bulk-insulating topological insulators and spin-helical Dirac fermion topological surface
transport.
Three-dimensional (3D) topological insulators (TI) are a novel class of electronic materials with
topologically-nontrivial band structure such that the bulk is gapped and insulating yet the surface
has topologically protected gapless conducting “topological surface states” (TSS) of helically spin
polarized Dirac fermions. Practically, it has often been challenging to unambiguously access and
study the transport properties of TSS in many realistic TI materials due to non-negligible bulk
conducting states. I will discuss our experimental demonstration of various high-quality “intrinsic”
TIs in the (Bi,Sb)2(Te,Se)3 family --- in the form of bulk crystals, exfoliated films and nanoribbons
--- with insulating bulk and surface-dominated conduction that allow us to reveal a number of
characteristic quantum transport properties of spin-helical Dirac fermion topological surface states,
such as the “half-integer” quantum Hall effect, “half-integer” Aharonov-Bohm effect, as well as
current-induced helical spin polarization. Our dual gated devices in TI films where both top and
bottom surfaces can be independently controlled realize an intriguing fully-tunable “two-species”
Dirac fermion systems where the degeneracy, coupling/hybridization and interaction between the
two species are all tunable by the film thickness and independent gating on the individual surfaces.
Interfacing with superconductors and other 2D materials such as graphene opens new possibilities
to explore topological superconductivity and other proximity induced topological states in hybrid
systems involving such high quality TIs.
Sang Wook Cheong, Rutgers University, Department of Physics and Astronomy
Charge compensation at polar or ferroelectric interfaces.
Polar interfaces in ferroelectrics and heterostructured films such as LAO/STO can be conducting,
and sometime superconducting. The localized charges at polar interfaces can be compensated
by charge carriers, additional polar charges or chemical defects such as oxygen vacancies. Various
mechanisms of this charge compensation will be discussed.
Manish Chhowalla, Rutgers University, School of Engineering
Phase Engineered Transition Metal Dichalcogenides for Energy and Electronics.
Two-dimensional transition metal dichalcogenides (2D TMDs) — whose generalized formula is MX2,
where M is a transition metal of groups 4–7 and X is a chalcogen — consist of over 40 compounds.
Complex metal TMDs assume the 1T phase where the transition metal atom coordination is
octahedral. The 2H phase is stable in semiconducting TMDs where the coordination of metal
atoms is trigonal prismatic. High performance of electronic and opto-electronic devices have been
demonstrated with semiconducting TMDs while interesting condensed matter effects such as
charge density waves and superconductivity have been observed in bulk metallic 1T phase TMDs.
However, stability issues have hampered the study of interesting phenomena in two-dimensional
1T phase TMDs. Recently there has been a surge of activity in developing methodology to reversibly
convert 2D 2H phase TMDs to 1T phase. In contrast with typical phase transformation conditions
involving pressure and temperature, phase conversion in TMDs involves transformation by
chemistry at room temperature and pressure. Using this method, we are able to convert 2H phase
2D TMDs to the 1T phase or locally pattern the 1T phase on 2H phase 2D TMDs. The chemically
converted 1T phase 2D TMDs exhibit interesting properties that are being exploited for in
applications such as high performance field effect transistors. In this contribution, I will summarize
the key properties of 2D 1T phase TMDs and their applications for electronics.
Yi Cui, Department of Materials Science and Engineering, Stanford University; Stanford Institute
for Materials and Energy Sciences, SLAC National Accelerator Laboratory
Synthesis and Property Tuning of Two-Dimensional Layered Materials.
Two-dimensional (2D) layered materials host many interesting physical and chemical phenomena.
Their nanowires, nanoplates and nanofilms represent novel candidates to host those phenomena.
Here we present our study on chemistry and physics of 2D layered nanostructures. First, we have
synthesized a range of morphologies and their heterostructures. Second, we have developed a
new method of zero-valent intercalation which allows unprecedented high levels of various metal
intercalants inserted into the van der Waals gaps. The resulted optical properties and electrical
conductance change drastically. Third, we have fabricated single nanostructure electrical transport
devices and demonstrate novel interesting electronic properties.
Hong Ding, Institute of Physics, Chinese Academy of Sciences
New physics emerged from old materials.
[abstract missing]
M. I. Eremets, Max Planck Institute of Chemistry
High temperature conventional superconductivity.
Recently we found superconductivity with Tc >200 K in hydrogen sulfide at high pressures[1]
The superconductivity has been proved by observation of zero resistance, Meissner effect, and
isotope effect. X-ray diffraction studies[2] confirm
predicted cubic structure of the superconductive
phases[3]. Fig. 1 summarizes the pressure dependence of
superconducting temperature for hydrogen sulfide and
its isotope deuterium sulfide.
We will present recent results on further study of the
superconductivity in hydrogen sulfide and other hydrides
by different methods and compare the experimental
results with available theoretical calculations.
References: 1. Drozdov, A.P., et al., Conventional
superconductivity at 203 K at high pressures.Nature
2015. 525: p. 73-77. 2. Einaga, M., et al., Crystal Structure
of 200 K-Superconducting Phase of Sulfur Hydride.
Nature Physics, 2016. 3. Duan, D., et al., Pressureinduced metallization of dense (H2S)2H2 with high-Tc
superconductivity. Sci. Reports, 2014. 4: p. 6968.
Presentations
(CONTINUED)
Claudia Felser, Max Planck Institute of Chemical Physics for Solids
Heusler compounds: Tunable materials with non trivial topologies.
Heusler compounds are a remarkable class of materials with more than 1,000 members and a wide
range of extraordinary multifunctionalities [1] including tunable topological insulators (TI) [2]. The
tunabilty of this class of materials is exceptional and nearly every functionality can be designed [1]
ranging from wide band gap semiconductors to hard magnetic ferrimagnetic metals. There are two
classes of Heusler compounds: half Heusler XYZ and Heusler X2YZ compounds, where Z is a main
group metal and X and Y are transition metals. Many of the XYZ compounds are semiconductors
or topological semimetals [2]. The ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and
LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from
superconductivity (for example LaPtBi) to magnetism (for example GdPtBi) and heavy fermion
behavior (for example YbPtBi). These properties can open new research directions in realizing the
quantized anomalous Hall Effect and topological superconductors. C1b Heusler compounds have
been grown as single crystals and as thin films. The control of the defects, the charge carriers and
mobilities can be optimized [3]. The band inversion was observed by angle resolved photoemission
spectroscopy [4]. Dirac cones and Weyl points can occur at the critical points in the phase diagrams
of TI or can be induced via a magnetic field in all magnetic Heusler compounds with an inverted
band structure [5].
Co2YZ and Mn2YZ Heusler compounds play an important role for future spintronic devices because
of their half-metallic band structure [1]. Recently a high spinpolarisation for spintronic applications
was proven by spin resolved photoemission [6]. The Curie temperature are far above room
temperature, up to 1200 K. Recently Co2TiSn and other Co2-Heusler compounds were found to be
Weyl semimetals [7]. Manganese-rich Heusler compounds are attracting interest in the context
of spin transfer torque based data storage [8,9], spin Hall effect, non collinear magnetism [10]
and rare-earth free hard magnets. The Mn3+ ions in Mn2YZ cause a Jahn Teller distortion [8,11].
Tetragonal Heusler compounds with large magneto crystalline anisotropy can be easily designed by
positioning the Fermi energy at a van Hove singularity in one of the spin channels. Because of the
ferrimagnetic arrangement of the sublattices, artificial antiferromagnets can be designed in Mn2YZ
Heusler compounds. New properties can be observed such as, large exchange bias, non-collinear
magnetism topological Hall effect, spin gapless semiconductivity and Skyrmions [10, 12-14]. Weyl
points and the corresponding Berry phase induce in Mn3Ge a giant anomalous Hall effect [15, 16].
References: [1] Graf, et al., Progress in Solid State Chemistry 39 1 (2011). [2] Chadov, et al., Nature
Mater. 9,541 (2010) and Lin, et al., Nature Mater. 9, 546 (2010). [3] Shekhar, et al., Physical Review B
86 155314 (2012). [4] Liu, et al., Nature Communication accepted, arXiv:1602.05633. [5] Hirschberger et al. Nature Mat. 2016 arXiv:1602.07219; C. Shekhar, et al. arXiv: 1604.01641. [6] Jourdan, et al, Nature Com. 5 3974 (2014). [7] Wang et al., arXiv:1603.00479, J. Kübler and C. Felser
Europhys. Lett. 114 (2016) 47005. [8] Winterlik, et. al., Adv. Mat. 24 6283 (2012). [9] Jeong, et al.,
Nature Com. 7 10276 (2016). [10] Meshcheriakova, et al., Phys. Rev. Lett. 113 087203 (2014). [11]
Wollmann, et al. Phys. Rev. B 92 064417 (2015). [12] Nayak, et al. Phys. Rev. Lett. 110 127204 (2013).
[13] Ouardi, et al., Phys. Rev. Lett. 110100401 (2013). [14] Nayak, et al., Nat. Mater. 14679 (2015).
[15] Kübler and Claudia Felser EPL 108 (2014) 67001. [16] Nayak, et al., Science Advances 2 (2016)
e1501870, Nakatsuji,et al. Nature 527 (2015) 212.
John W. Freeland, Advanced Photon Source, Argonne National Laboratory
Non-equilbrium phases of nickelate heterostructures: From visualizing synthesis to driven
dynamics.
Oxide heterostructures offer new opportunities to control the phases of strongly correlated
electrons and to seek out phases that do not exist in the bulk counterparts[1]. Through the
utilization of strain, confinement, interfacial charge transfer, and putting distinct phases in close
proximity, one can create new boundary conditions in the search for new quantum many-body
phenomena. Nickelates are one such class of materials that display a metal-insulator transition
connected with magnetic and charge order. Heterostructures of these materials have shown many
opportunities for control of these different degrees of freedom with strain and confinement[2].
In this talk I will focus on the non-equilibrium properties to understand how to manipulate these
materials in new ways. In the first part, I will highlight our recent work on how the polar mismatch
between layers is resolved for the case of ultrathin LaNiO3 layers. The second part will focus on
driving phase transitions with ultrafast optical pulse to understand the behavior and how to
manipulate different degrees of freedom on ultrafast timescales. In both cases, we are using the
connection between advanced X-ray probes and theory to not only create a framework for rational
materials design, but will also touch on our recent work to expand our understanding of how these
phase diagrams change as we move from the static to the dynamical realm with the goal of creating
new materials that can be efficiently manipulated with external perturbations.
Acknowledgements: Work at Argonne is supported by the U.S. Department of Energy, Office of
Science, under Contract No. DE-AC02-06CH11357.
References: [1] J. Chakhalian, J.W. Freeland, et. al. Rev. Mod. Phys. 86, 1189 (2014). [2] S. Middey et.
al., Ann. Rev. of Mat. Res. 46, 305 (2016).
Nuh Gedik, Massachusetts Institute of Technology
Shining light on Topological Insulator.
The topological insulator (TI) is a new phase of matter that exhibits quantum-Hall-like properties,
even in the absence of an external magnetic field. Understanding and characterizing unique
properties of these materials can lead to many novel applications such as current induced
magnetization or extremely robust quantum memory bits. In this talk, I will discuss recent
experiments in which we used novel time and angle-resolved photoemission spectroscopy (ARPES)
to directly probe and control properties of Dirac Fermions in TIs.
The unique electronic properties of the surface electrons in a topological insulator are protected by
time-reversal symmetry. Breaking such symmetry without the presence of any magnetic ordering
may lead to an exotic surface quantum Hall state without Landau levels. Circularly polarized light
naturally breaks time-reversal symmetry, but achieving coherent coupling with the surface states is
challenging because optical dipole transitions generally dominate. Using time- and angle-resolved
photoemission spectroscopy, we show that an intense ultrashort mid-infrared pulse with energy
below the bulk band gap hybridizes with the surface Dirac fermions of a topological insulator to
form Floquet-Bloch bands. The photon-dressed surface band structure is composed of a manifold
of Dirac cones evenly spaced by the photon energy and exhibits polarization-dependent band
gaps at the avoided crossings of the Dirac cones. Circularly polarized photons induce an additional
gap at the Dirac point, which is a signature of broken time-reversal symmetry on the surface. These
observations establish the Floquet-Bloch bands in solids experimentally and pave the way for
optical manipulation of topological quantum states of matter.
Ke He, State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua
University
Searching for materials that show the quantum anomalous Hall effect at higher temperature.
The quantum anomalous Hall (QAH) effect is a quantum Hall effect induced by spontaneous
magnetization instead of an external magnetic field. The effect occurs in two-dimensional (2D)
insulators with topologically nontrivial electronic band structure characterized by a non-zero Chern
number. The experimental observation of the QAH in thin films of magnetically doped topological
insulators (TIs) paves the ways for practical applications of dissipationless quantum Hall edge
Presentations
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states and for realizations of the novel quantum phenomena, but a temperature as low as 30 mK
is required to reach a perfect quantization. Further studies in these directions require magnetic TI
materials that can show the QAH effect at higher temperature. We have performed systematic study
on the QAH effect in magnetically doped TI films with different thicknesses, magnetic dopants and
compositions [2,3]. The results clarify the relations between the QAH effect and the energy band
structure, electronic localization and ferromagnetism of a magnetic TI film and provide insights into
designing and fabrication of high temperature QAH materials.
References: [1] C. -Z. Chang et al., Science 340, 167 (2013). [2] X. Feng et al., Adv. Mater. DOI:
10.1002/adma.201600919 (2016). [3] Y. Ou et al., APL Mater. DOI: 10.1063/1.4960111 (2016).
Harold Y. Hwang, Departments of Applied Physics and Photon Science, Stanford University and
SLAC National Accelerator Laboratory
Complex Oxides in the 2D Limit.
The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had
transformative impact on science and technology. In parallel with the exfoliation and stacking of
intrinsically layered crystals, the atomic-scale thin film growth of complex materials, not limited to
layered systems, has enabled the creation of artificial 2D heterostructures with novel functionality
and emergent phenomena, as seen in perovskite heterostructures. While offering new degrees of
freedom, the requirement of a substrate limits the capability to manipulate these heterostructures
as utilized in exfoliated materials. Here we present a general method to create freestanding
perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite
substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline
membranes are produced by etching the Sr3Al2O6 layer in water and transferred to arbitrary
substrates, providing the opportunity to integrate them with heterostructures of semiconductors
and layered compounds.
Sergei V. Kalinin, Institute for Functional Imaging of Materials and The Center for Nanophase
Materials Sciences, Oak Ridge National Laboratory
Big, deep, and smart data in atomically resolved imaging: a bridge to accelerating materials
by design.
The development of electron and scanning probe microscopies in the second half of XX century
have produced spectacular images of internal structure and functionalities of matter with
nanometer and now atomic resolution. Much of this progress since 80ies was enabled by computerassisted methods for data acquisition and analysis that provided automated analogs of classical
storage methods. However, the progress in imaging technologies since the beginning of XXI
century has opened the veritable floodgates of high-veracity information on atomic positions and
functionality, often in the form of multidimensional data sets containing partial or full information
on atomic positions, functionalities, etc. In this presentation, I will discuss the research activity
coordinated by the Institute for Functional Imaging of Materials (IFIM), namely pathways to bridge
imaging and theory via big data technologies to enable design of new materials with tailored
functionalities. This goal will be achieved first through a big data approach – i.e., developing
pathways for full information retrieval and exploring correlations in structural and functional
imaging. In electron microscopy, the big data approaches are illustrated by full data acquisition in
ptychography and real-space crystallographic mapping. These techniques can be further extended
to develop structure property relationships on atomic levels, allowing direct data mining of
multimodal structural, chemical, and functional data and creating a library of atomic configurations
and associated properties. A deep data approach will allow merging this knowledge with physical
models, providing input into the Materials Genome program and enabling a new paradigm for
materials research based on theory-experiment matching of microscopic degrees of freedom.
Finally, a smart data approach will enable algorithms for data identification, expert assessment, and
ultimately, control over matter.
Acknowledgements: This research is supported by the by the U.S. Department of Energy, Basic
Energy Sciences, Materials Sciences and Engineering Division, and was conducted at the Center
for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the
Scientific User Facilities Division, BES DOE.
References: 1. S. Jesse, Q. He, A.R. Lupini, D.N. Leonard, M.P. Oxley, O. Ovchinnikov, R. Unocic, A.
Tselev, M. Fuentes-Cabrera, B.G. Sumpter, S.J. Pennycook, S.V. Kalinin, and A.Y. Borisevich, Atomiclevel sculpting of crystalline oxides: towards bulk nanofabrication with single atomic plane
precision, Small 11, 5895 (2015). 2. Sergei V. Kalinin, Bobby G. Sumpter, and Richard K. Archibald,
Big-deep-smart data in imaging for guiding materials design, Nature Materials 14, 973 (2015). 3. B.G.
Sumpter, R.K. Vasudevan, T. Potok, and S.V. Kalinin, A Bridge for Accelerating Materials by Design,
NPJ Comp Mat, 15008 (2015).
Gertjan Koster, University of Twente
Control of interfacial octahedral rotations in oxide heterostructures.
In this presentation we will discuss how to manipulate magnetic and electronic anisotropic
properties in thin film heterostructures by engineering the oxygen network on the unit-cell level.
In addition, we show that for some substrate/film combinations, the symmetry change induced
at the interface can propagate for unusual thicknesses. The strong oxygen octahedral coupling is
found to transfer the octahedral rotation present in the NdGaO3 (NGO) substrate to ferromagnetic
La2/3Sr1/3MnO3 (LSMO) films in the interface region. This causes an unexpected realignment of
the magnetic easy axis along the short axis of the LSMO unit cell as well as the presence of a giant
anisotropic transport in these ultrathin LSMO films. As a result we possess control of the lateral
magnetic and electronic anisotropies by atomic scale design of the oxygen octahedral rotation.
Young Hee Lee, Center for Integrated Nanostructure Physics, Institute for Basic Science,
Sungkyunkwan University
Phase transition engineering of 2D layered materials.
Motivated by graphene which has exotic Dirac-particle like feature with extremely high mobility at
room temperature but still limited by the zero bandgap feature, other types of 2D materials such as
insulating hexagonal-BN monolayer and semiconducting layered transition metal dichalcoginides
(LTMDs) have been intensively focused as a new class of flexible and semiconducting materials.
These materials have known to exhibit exotic physical and chemical phenomena which have never
been accessed with 3D materials. I will demonstrate some key concept of 2D materials why they
differ from 3D and show some examples of some new phenomena that emerge uniquely in 2D
materials in this talk. We will also demonstrate that thin MoTe2 revealed a reversible phase transition
from 2H to 1T’ at around 650-900oC depending on Te-rich conditions. We will further demonstrate
that the phase transition of MoTe2 can be provoked by several robust parameters such as laser
irradiation and strain. The problematic Ohmic contact was realized by phase patterning of the
contact area at source and drain positions with laser irradiation. We further demonstrate that even
the phase transition temperature can be reduced to room temperature by applying a tensile strain
of ~0.2%. In addition, electronic metal-insulator phase transition will be described via quantumfluctuation vs percolation.
References: 1. Keum and Cho et al., Bandgap opening in few-layered monoclinic MoTe2 ', Nature
Phys. 11, 482-486 (2015). 2. Cho et al., ' Phase patterning for ohmic homojunction contact in MoTe2
', Science 349, 625-628 (2015). 3. Song et al., ‘Room-Temperature Semiconductor-metal Transition of
MoTe Thin Film Engineered by Strain', NanoLett. 16, 188 (2016).
Presentations
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Antoine Maignan, Laboratoire CRISMAT CNRS/ENSICAEN/UCBN
David Berthebaud, Ramzy Daou, Oleg Lebedev, Emmanuel Guilmeau and Sylvie Hébert
AMX2 layered materials (M= transition metal ; X = O, S, Se): from thermoelectrics to
multiferroics through 2D metals.
The layered structure of dichalcogenides allows the thermal conductivity to be engineered as in
TiS2 [1,2]. For the latter, by intercalating foreign elements such as Cu or Co or Ag between successive
TiS2 slabs, it is possible to inject charge carriers and simultaneously reduce the lattice part of the
thermal conductivity ĸ (Fig1). In contrast to Ti, the CrS2 dichalcogenide does not form, but this
CdI2-type layer is stabilized in AgCrS2, a multiferroic with a 4SL antiferromagnetic structure [3]. The
isostructural selenide, AgCrSe2, though it exhibits a cycloidal magnetic structure, is an interesting
thermoelectric. Low temperature inelastic neutron scattering experiments revealed a very low
frequency mode at 3 meV, ascribed to large anharmonic displacements of the Ag+ ions in the [Ag]∞
layer. The low thermal conductivity of AgCrSe2 is thus attributed to acoustic phonon scattering by a
regular lattice of Ag+ oscillating in quasi-2D potential wells [4]. Interestingly, the oxides derived from
the delafossite show similar extreme properties, i.e. 2D metals in the case of PdCoO2 and PdCrO2
[5,6], with large thermal conductivities, or insulating with multiferroics properties for the CuCrO2
antiferromagnet [7].
All these properties illustrate the potentialities of
these 2D materials where two layers of different types
are naturally intergrown in a 1:1 manner and where
the metal network is triangular. In the presentation, a
comparison will be made between AMX2 compounds
to sort the important features needed for properties
enhancement.
Fig1. Thermal conductivity at 700K (left y-axis) and
lattice part of the thermal conductivity (right y-axis)
as a function of the nominal content x of Cu (or
Ag) according to the CuxTiS2 and AgxTiS2 chemical
formulas.
References: 1. E. Guilmeau et al, Physical Chemistry
Chemical Physics 17, 24541 (2015). 2. R. Daou et al, Journal of Applied Physics 117, 165101 (2015).
3. F. Damay et al, Phys. Rev B 83, 184413 (2011). 4. F. Damay et al, Scientific Report 6, 23415 (2016).
5. R. Daou et al, Phys. Rev B 91, 041113 (2015). 6. R. Daou et al, Phys. Rev B 91, 245115 (2015). 7. M.
Poienar et al, Phys. Rev B 79, 014412 (2009).
J. Mannhart, Max Planck Institute for Solid State Research
B. Prasad, G. Pfanzelt, J. Mannhart
Novel Quantum-Matter Heterostructures.
We will present our exploration of quantum heterostructures comprising new types of materials to
provide desirable functions that were up to now not attainable.
John Mitchell, Materials Science Division, Argonne National Laboratory
High Pressure Zone Growth of Correlated Electron Oxides.
Competition between localized and itinerant electrons in highly correlated materials can lead
to myriad insulating ground states, including spatially inhomogeneous but ordered charge
superlattices. In layered transition metal oxides, such charge order can take the form of stripes,
which typically arrange themselves in staggered formations to reduce Coulomb repulsion. We show
using synchrotron x-ray diffraction on high-pO2 floating-zone grown single crystals of the layered
nickelate La4Ni3O8 that this transition is driven by a real space ordering of charge into a quasi-2D
charge stripe ground state. The charge stripe superlattice propagation vector corresponds with that
found in the related 1/3-hole doped single layer Ruddlesden-Popper nickelate, La5/3Sr1/3NiO4 (LSNO1/3, Ni2.33+) with orientation at 45° to the Ni-O bonds, speaking to the universality of stripe structure
set by charge concentration. Surprisingly, we find that the charge stripes within each trilayer of
La-438 are stacked in phase from one layer to the next, at odds with any simple Coulomb repulsion
argument. We discuss a possible lattice-driven explanation for this stripe stacking as well as
comment on how La-438 is a better approximant to cuprates than the single layer nickel oxides. We
also speak briefly on the power of high fugacity synthesis for discovering new transtion metal oxide
quantum materials.
Tsutomu Miyasaka, Graduate School of Engineering, Toin University of Yokohama
Interfacial management of hybrid perovskite solar cells toward high performance and
stability.
Organo-lead halide perovskite compounds exhibit many rare functions as narrow bandgap
semiconductors which are superior in applications for photovoltaic power conversion as well
as for high gain photon-mode detection of visible light. On the start of our research in 2006,
power conversion efficiencies (PCE) up to 2.2 % were obtained by using CH3NH3PbX3 (X=Br, I) as
an absorber on mesoporous TiO2 in junction of liquid redox electrolytes.1a In 2008, this method
was applied to make a solid-state perovskite-based PV cell by using carbon-polymer conductive
composite as a hole transport material.1b Recent rapid progress in PCE by improving the quality
and stability of perovskite crystal layers has enabled PCE to reach beyond 22%. Our group has been
tackling the cell fabrication process mostly by low-temperature printing processes and achieved
>17%.2 We have also investigated the origin of hysteretic I-V behavior by focusing interfacial
structure defects and their influence on cell stability under light soaking.3
Low temperature printing process (<120oC) can be applied to high performance perovskite cells,
by using ZnO, SnO2, brookite TiO2, etc. as mesoporous electron collectors. ZnO/SnO2 composite
enabled good cell performance with PCE>15% and long cell life (>months) without encapsulation.4
Brookite TiO2 is especially unique in terms of strong interparticle necking by dehydration
condensation reaction that enables formation of dense uniform layer. Thin plastic film-based flexible
perovskite device was fabricated with methylammonium (MA) perovskite. With non-hysteretic
PCE>14% it shows stable performance against mechanical bending over 100 times.5 Brookite TiO2
is also useful in making high performance and heat resistance cells on glass by using formamidium
(FA)-based mixed halide perovskite, FA0.85MA0.15Pb(I0.85Br0.15)3, which work with efficiency >18%.
Enormous potential of perovskite-based device is not only for power devices but also for high
performance optical sensing. Such additional but equally notable functions of CH3NH3PbI3 are also
enabled by strong light absorption and activity of long-lived photocarrier for high yield quantum
conversion. As a photodiode, gain of CH3NH3PbI3-induced photocurrent was found to reach a
level of the order of 103, showing excellent light-switching performance.6 Such rare functions
of the perovskite as a hybrid semiconductor material provide a lot of rooms for us to explore in
photovoltaics and optoelectronics. Lead-free environmentally benign material to replace lead halide
perovskite is also an importance subject of material design. We recently showed Bi-based material
such as (CH3NH3)3Bi2I9 as a candidate of solution-printable semiconductor.7 This is a direction of
material solution towards next generation perovskite solar cell development.
References: 1. a) A. Kojima, T. Miyasaka, et al. Abstract #352, 212th ECS Meeting, Washington, USA,
October, 2007, b) ibid. PRiME 2008, Abstract #27, Honolulu, Hawaii, October 2008. 2. T. Miyasaka,
Chem. Lett. 2015, 44, 720-729. 3. A. K. Jena, A. Kulkarni, M. Ikegami, T. Miyasaka, J. Power Sources,
2016, 309, 1-10. 4. J. Song, E. Zheng, X.-F. Wang, W. Tian, T. Miyasaka, Solar Ener. Mat. Solar Cells,
2016, 144, 623-630. 5. A. Kogo, M. Ikegami, T. Miyasaka, Chem. Commun., 2016, 52, 8119-8122. 6. H.W. Chen, N. Sakai, A. K. Jena, Y. Sanehira, M. Ikegami, K.-C. Ho, T. Miyasaka, J. Phys. Chem. Lett. 2015,
6, 1773 -1779. 7. T. Singh, A. Kulkarni, M. Ikegami, T. Miyasaka, ACS Appl. Mater. Interfaces, 2016, 8,
14542-14547.
Presentations
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Jagadeesh S. Moodera, 1Physics Department, 2Francis Bitter Magnet Lab, 3Plasma Science and Fusion
Center, Massachusetts Institute of Technology
In collaboration with: At MIT, CuiZu Chang,2,3 Ferhat Katmis, 1.2,3 Peng Wei. 1,2,3; At Penn State U,
W-W. Zhao, D. Y. Kim, C-x. Liu, J. K. Jain, M. H. W. Chan; At Oakridge National Lab, V. Lauter; From
Northeastern U., B. A. Assaf, M. E. Jamer, D. Heiman; At Argonne Lab, J. W. Freeland; At Saha Institute
of Nuclear Physics (India), B. Satpati.
Quantum anomalous Hall state and dissipationless chiral conduction in topological insulator
thin films with broken time reversal symmetry.
Most of the exotic quantum phenomena predicted in a topological insulator (TI) needs to have
broken time reversal symmetry (TRS) by ferromagnetic perturbation of their Dirac surface states.
The quantum anomalous Hall (QAH) effect and dissipationless quantized Hall transport are two of
the very important predictions in these systems. Besides growing high quality TI thin films, ideal
magnetic doping and tuning of Fermi to the exchange gap is required. The realization of the QAH
effect in realistic materials requires ferromagnetic insulating materials that have topologically nontrivial electronic band structures. In a TI, the ferromagnetic order and TRS breaking is achievable
through doping with a magnetic element or via ferromagnetic proximity coupling with a
magnetic material. Our both experimental approaches showed excellent results along with some
unanticipated observations: the proximity induced magnetism in TI exhibited stability far above the
expected temperature range. We will discuss the robust QAH state and dissipationless chiral edge
current flow achieved in a hard ferromagnetic TI system.1,2 This could be a major step to lead us
towards dissipationless electronic applications, making such devices more amenable for metrology
and spintronics applications. Furthermore, our study of the gate and temperature dependences of
transport measurements may elucidate the causes of the dissipative edge channels and the need
for very low temperature to observe QAH.
Acknowledgements: Work supported by NSF Grant DMR-1207469, the ONR Grant N00014-13-10301, and the STC Center for Integrated Quantum Materials under NSF grant DMR-1231319.
References: 1. P. Wei et al., Phys. Rev. Lett. 110, 186807 (2013) . 2. C-Z Chang et al., Nat. Matl. 13, 473
(2015); Phys. Rev. Lett. 115, 057206 (2015). 3. F. Katmis et al., Nature (to be published, May 2016).
Margaret Murnane, Department of Physics and JILA, University of Colorado and NIST, Boulder
Cong Chen1*, Zhensheng Tao1*, Tibor Szilvási2, Mark Keller3, Manos Mavrikakis2, Henry Kapteyn1
1Department of Physics and JILA, University of Colorado and NIST, Boulder; 2Department of Chemical
and Biological Engineering, University of Wisconsin-Madison; 3National Institute of Standards and
Technology (NIST)
Direct Time-Domain Observation of Attosecond Electron Dynamics in Occupied Bands in
Solids.
We use attosecond pulse trains to directly measure photoelectron lifetimes in Ni(111) and Cu(111).
We observe a strong influence of material band structure on the measured lifetimes, which reveal
attosecond timescale electron screening and scattering.
Tabletop high-harmonic generation (HHG) produces attosecond pulse trains with the unique
characteristics of good energy resolution (≈100-300meV) and sub-fs time resolution, making
HHG an ideal source for time-resolved photoemission studies [1, 2]. In combination with angleresolved photoemission spectroscopy (ARPES), it is now possible to extract detailed information
about dynamic band dispersion over the entire Brillouin zone. In recently published work [3] taking
advantage of laser-assisted photoemission, we harnessed attosecond pulse trains to directly and
unambiguously measure the difference in lifetimes between photoelectrons born into free-electronlike states and those excited into unoccupied excited states in the band structure of nickel(111). A
significant increase in lifetime of 212±30 as occurs when the final state coincides with an unoccupied
excited state in the Ni band structure. Moreover, a strong dependence of lifetime on emission angle is
directly related to the final-state band dispersion as a function of electron transverse momentum.
In this new work, we directly extract initial-state attosecond time delays associated with the
photoemission process itself from Ni and Cu, By harnessing the high energy resolution of attosecond
pulse trains combined with polarization- and angle-resolved photoemission, we can clearly
distinguish different photoelectron lifetimes from individual occupied valence bands of Ni and Cu
with unprecedented energy and time resolution.This allows us to distinguish different electron
screening and scattering timescales in Ni(111) and Cu(111) in the time domain for the first time. We
note that our results are distinctly different from previous time-delay measurements in solids, in
which multiple valence bands were probed using broad bandwidth isolated attosecond pulses, thus
necessarily integrating over multiple bands and photoemission features [2].
References: [1] S. Eich et al., “Time- and angle-resolved photoemission spectroscopy with optimized
high-harmonic pulses using frequency-doubled Ti:Sapphire lasers”, J. Electron Spectrosc. Relat.
Phenom. 195, 231–236 (2014). [2] A. L. Cavalieri et al., “Attosecond spectroscopy in condensed matter,”
Nature 449, 1029–1032 (2007). [3] Z. Tao et al., “Direct time-domain observation of attosecond finalstate lifetimes in photoemission from solids”, Science 353, 62 (2016).
*Correspondence should be addressed to [email protected], [email protected].
Shuji Nakamura, Materials and ECE Departments, Solid State Lighting and Energy Center,
University of California - Santa Barbara
The invention of high efficient blue LEDs and future Solid State lighting.
In 1970's and 80’s, an efficient blue and green light-emitting diodes (LED) were the last missing
elements for solid-state display and lighting technologies due to the lack of suitable materials. By
that time, III-nitride alloys was regarded the least possible candidate due to various "impossible"
difficulties. However, a series of unexpected breakthroughs in 1990's totally changed people's view
angle. Finally, the first high efficient blue LEDs were invented and commercialized at the same time
of 1993. Nowadays, III-nitride-based LEDs have become the most widely used light source in many
applications. The LED light bulbs are more than ten times efficient than incandescent bulb, and
they last for 50 years! At their current adoption rates, by 2020, LEDs can reduce the world’s need for
electricity by the equivalent of nearly 60 nuclear power plants.
The history of the invention of blue LED and future lighting will be described.
Tae Won Noh, Center for Correlated Electron Systems, Institute for Basic Science; Department of
Physics and Astronomy, Seoul National University
Expanding phase diagram of BaBiO3 via controlling thickness and doping.
Recently, we found a novel route to experimentally control the phase diagram in the perovskite
bismuthate BaBiO3 (BBO), the parent compound of several high-Tc oxide superconductors [1,2].
Numerous experimental and theoretical studies have sought to gain insight into the mechanisms
that control the physics of these bismuthates; to date, however, only limited progress has been made
in hole-doped bulk samples. Here, we present our recent progress on exploration of the novel phase
diagram of BBO via thickness and doping controls. We revealed that a minimum length scale to
sustain a charge density wave order in BBO films by thickness control [3]. Furthermore, the electronic
and structural properties of BBO were strongly dependent on oxygen deficiency, disclosed by the
combination of in situ spectroscopic techniques and first-principles calculations. Our approaches
introduce independent control parameters to explore the BBO phase diagram, and may also provide
a useful guideline to study the recently predicted topological phases in electron-doped bismuthates
[4].
Presentations
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References: [1] A. W. Sleight, J. L. Gillson, P. E. Bierstedt, Solid State Commun. 17, 27 (1975). [2] R. J.
Cava et al., Nature 328, 814 (1988). [3] G. Kim et al., Phys. Rev. Lett. 115, 226402 (2015). [4] B. Yan et
al., Nat. Phys. 9, 709 (2013).
Seongshik Oh, Department of Physics and Astronomy, Rutgers University
Materials issues in topological materials.
Defects in topological insulators (TIs) have significant impact on the properties of TIs. Like other
layered chalcogenides, TIs have relatively weak bonding energies between the elements and
accordingly, they tend to suffer from high density of native defects. Due to the high density of
native defects, all intrinsic TIs suffer from severe conduction problem: if such defects were absent,
TIs would have fully insulating bulk state with a band gap of ~0.3 eV. Although much of these
defects can be suppressed via various compensation doping schemes, when these samples are
made thin, interfaces tend to generate much more defects than are expected from their bulk
properties. These additional interfacial defects push, otherwise insulating, bulk state to be highly
conducting again. These observations suggest that despite the general expectation that TIs and
other layered chalcogenide materials should have relatively low interfacial defect density due to the
van der Waals nature of their interlayer bonding, they actually are quite susceptible to high density
of interfacial defects. We will discuss these defect problems and their potential solutions in TIs and
other topological materials.
Johnpierre Paglione, Center for Nanophysics and Advanced Materials, Department of Physics,
University of Maryland
Hyunsoo Kim1, Kefeng Wang1, Yasuyuki Nakajima1, Rongwei Hu1, Steven Ziemak1, Paul Syers1, Limin
Wang1, Halyna Hodovanets1, Jonathan D. Denlinger2, Philip M. R. Brydon3,4, Daniel F. Agterberg5,
Makariy A. Tanatar6, Ruslan Prozorov6, and Johnpierre Paglione1.
1Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland;
2Advanded Light Scource, Lawrence Berkeley National Laboratory; 3Condensed Matter Theory Center
and Joint Quantum Institute, Department of Physics, University of Maryland; ⁴Department of Physics,
University of Otago; ⁵Department of Physics, University of Wisconsin; ⁶Ames Laboratory, Department of
Physics and Astronomy, Iowa State University
Topology, magnetism and high-spin superconductivity in half-Heusler semimetals.
The ternary XYZ half-Heusler series of materials spans the periodic table and harbors a plethora of
interesting ground states. In the strong spin-orbit systems RPdBi and RPtBi (R : rare earth), tuning
of the rare earth f-electron component allows for simultaneous control of both lattice density
via lanthanide contraction, as well as the strength of magnetic interaction via de Gennes scaling,
allowing for a unique tuning of both the normal state band inversion strength, superconducting
pairing and magnetically ordered ground states. Antiferromagnetism occurs below a Néel
temperature that scales with de Gennes factor, while a superconducting transition is simultaneously
linearly suppressed. With superconductivity appearing in a system with non-centrosymmetric
crystallographic symmetry and topological electronic structure, the possibility of Cooper pairing
with higher angular momentum (i.e. beyond triplet) and non-trivial topology provides a unique and
rich opportunity to realize both predicted and new exotic excitations in topological materials.
We will discuss recent measurements in YPtBi that provide strong evidence for the realization of a
nodal superconducting gap as a consequence of mixing a conventional pairing state with higher
angular momentum states.
Jason Petta, Princeton University
Isotopically enriched materials for quantum computing.
Isotopically enriched silicon has been termed a “semiconductor vacuum” due to its ability to support
seconds long quantum coherence times. I will describe recent efforts by my group to couple a
single electron trapped in a Si/SiGe double quantum dot to the photonic field of a superconducting
coplanar waveguide resonator. A high degree of control over a single electron wavefunction
is achieved using a recently developed overlapping aluminum gate electrode architecture.
Measurements of the microwave transmission through the superconducting resonator allow
sensitive measurements of the charge state occupation of the Si/SiGe double quantum dot.
Ramaoorthy Ramesh, Department of Materials Science and Engineering, University of California,
Berkeley; Department of Physics, University of California, Berkeley; Materials Sciences Division,
Lawrence Berkeley National Laboratory
Observation of Polar Vortices in Oxide Superlattices.
The complex interplay of spin, charge, orbital, and lattice degrees of freedom has provided for a
plethora of exotic phase and physical phenomena1,2,3,4,5. Among these, in recent years, topological
states of matter and spin textures have emerged as fascinating consequences of the electronic band
structure and the interplay between spin and spin-orbit coupling in materials6,7. In this work, we
leverage the competition between charge, orbital, and lattice degrees of freedom in superlattices
of PbTiO3/SrTiO3 to produce complex, vortex-antivortex pairs (that exhibit smoothly varying
ferroelectric polarization with a 10 nm periodicity) that are reminiscent of topological features such
as skyrmions and merons6. Using a combination of advanced layer-by-layer growth techniques,
atomic-resolution mapping of structure and local polar distortions using scanning-transmission
electron microscopy, and phase-field modeling approaches we present a comprehensive picture of
the nature of the varying polarization profile in such vortex states. The continuous rotation of the
polar state into the vortex structures is thought to occur from an interplay of polar discontinuities
at the PbTiO3/SrTiO3 interface (where ν∙P ≠0), the phase transformation strain and gradient energy
in the PbTiO3 layer, and the strain imposed by the substrate. Finally, the implications of these
observations are discussed as they pertain to producing new states of matter and emergent
phenomena (such as chirality) in such superlattices.
M.J. Rosseinsky, Department of Chemistry, University of Liverpool
Design of Advanced Materials?
The development of advanced materials will increasingly rely on our ability to assemble complex
compositions in an ordered and predictable manner to generate enhanced properties. It is attractive
to harness the ever-increasing power of computation in the search for new materials. The scale and
nature of the problem make brute force de novo approaches challenging, while “big data” searches
for analogues of existing structures in databases cannot identify potentially transformative new
structures. Building chemical knowledge into computational tools used together with experiment
offers a different and complementary approach. I will present an example of crystal chemicallyinformed computational identification of a new solid oxide fuel cell cathode (1). This integrated
approach has recently allowed us to combine permanent magnetism and electrical polarisation in a
single phase material above room temperature (2), a major challenge in materials synthesis because
of the competing electronic structure requirements of these two ground states. As a counterpoint,
we have recently used a non-computational multiple length scale symmetry control strategy to
Presentations
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switch both of these long-range orders in a magnetoelectric multiferroic at room temperature (3).
This emphasises the enduring importance of developing the crystal chemical understanding that
drives “classical” approaches to materials design. Design of coherent interfaces between materials
with different crystal structures to permit layer-by-layer heterostructure growth is also discussed. (4)
References: (1) M. Dyer et al Science 340, 847, 2013. (2) M. Pitcher et al Science 347, 420, 2015. (3) P.
Mandal et al Nature 525, 363, 2015. (4) M. O’Sullivan et al Nature Chemistry 8, 347, 2016.
Darrell G. Schlom, Department of Materials Science and Engineering, Cornell University; Kavli
Institute at Cornell for Nanoscale Science
Tuning the Band Structure of Ruthenates with Strain and Dimensionality.
Ruthenates with perovskite and perovskite-related structures host a remarkably diverse class
of exotic quantum phases ranging from spin-triplet superconductivity, ferromagnetism,
metamagnetism, spin-density waves, antiferromagnetism, and quantum criticality—all with the
same basic building block of corner-sharing RuO6 octahedra containing Ru4+ ions. We exploit
strain engineering1 to tune the band structure of the complex oxide ruthenates: CaRuO3,2 SrRuO3,3
and BaRuO3,⁴ with the perovskite structure as well as their two-dimensional counterparts Sr2RuO⁴
and Ba2RuO4.⁵ The ruthenate films are grown by reactive molecular-beam epitaxy (MBE) and the
misfit strain is imposed by underlying substrates to strain these complex oxide thin films to percent
levels3—far beyond where they would crack or plastically deform in bulk. The band structure is
revealed by high-resolution angle-resolved photoemission (ARPES) on pristine as-grown surfaces of
these complex oxides made possible by a direct ultra-high vacuum connection between the MBE
and ARPES. Our work demonstrates the possibilities for utilizing strain engineering as a disorderfree means to manipulate emergent properties and many-body interactions in correlated materials.
References: 1. D.G. Schlom, L.Q. Chen, C.J. Fennie, V. Gopalan, D.A. Muller, X.Q. Pan, R. Ramesh, and
R. Uecker, “Elastic Strain Engineering of Ferroic Oxides,” MRS Bulletin 39 (2014) 118–130. 2. Y. Liu,
H. Nair, D. Baek, J.P.C. Ruff, L.F. Kourkoutis, D.G. Schlom, and K.M. Shen (unpublished). 3. D.E. Shai,
C. Adamo, D.W. Shen, C.M. Brooks, J.W. Harter, E.J. Monkman, B. Burganov, D.G. Schlom, and K.M.
Shen, “Quasiparticle Mass Enhancement and Temperature Dependence of the Electronic Structure
of Ferromagnetic SrRuO3 Thin Films,” Physical Review Letters 110 (2013) 087004. 4. B. Burganov, H.
Paik, J.P.C. Ruff, D.G. Schlom, and K.M. Shen (unpublished). 5.B. Burganov, C. Adamo, A. Mulder, M.
Uchida, P.D.C. King, J.W. Harter, D.E. Shai, A.S. Gibbs, A.P. Mackenzie, R. Uecker, M. Bruetzam, M.R.
Beasley, C.J. Fennie, D.G. Schlom, and K.M. Shen, “Strain Control of Fermiology and Many-Body
Interactions in Two-Dimensional Ruthenates,” Physical Review Letters 116 (2016) 197003.
Jian Shen, Fudan University
Manipulating Electronic Phase Separation in Complex Oxides.
For strongly correlated systems, it has been known that co-existence of electronic phases is often
energetically favored. Investigation of the so-called electronic phase separation (EPS) phenomena
is not only important for understanding the strong electronic correlations in these materials, but
also very useful for tuning their physical properties. In this work, we push this trend to its limit by
developing the capability of manipulating EPS in colossal magnetoresistance (CMR) manganites
systems. We demonstrate that it is possible to pattern the EPS in manganites and thus design the
physical properties of the systems. By doing so, we are able to gain a much deeper insight of the
physical origin of electronic phase separation in these materials.
Yuichi Shimakawa, Institute for Chemical Research, Kyoto University
Novel transition-metal oxides with unusual valence cations.
Unusual high valence states of cations like Fe4+ can be stabilized in some oxides synthesized under
strong oxidizing atmosphere. Two new A-site ordered perovskite-structure oxides containing
unusually high valence states of Fe, CaCu3Fe4O12 with Fe4+ and LaCu3Fe4O12 with Fe3.75+, were
recently obtained. The instabilities of the high valence states at low temperatures were relieved by
characteristic charge changes; by charge disproportionation (4Fe4+ > 2Fe3+ + 2Fe5+) in CaCu3Fe4O12,
and by intersite charge transfer between A-site Cu and B-site Fe ions (3Cu2+ + 4Fe3.75+ > 3Cu3+ + 4Fe3+)
in LaCu3Fe4O12 [1-2]. Those unusual charge changes occurred in three-dimensional networks of Fe
ions in the perovskite structures. Very recently, we found that a similar charge disproportionation to
that observed in CaCu3Fe4O12 occurred even in a two-dimensional layered arranged of Fe4+ in a new
layered double perovskite, Ca2FeMnO6 [3-4]. The behaviors in charge, spin, and lattice, in those novel
transition-metal oxides containing unusual high valence cations are discussed.
References: [1] W. -T. Chen, Y. Shimakawa, et al., Sci. Rep. 2, 449 (2012). [2]Y. Shimakawa (Review), J.
Phys. D: Appl. Phys. in press (2015). [3] Y. Hosaka, Y. Shimakawa, et al., Bull. Chem. Soc. Jpn. 88, 657
(2015). [4] Y. Hosaka, Y. Shimakawa, et al., J. Amer. Chem. Soc. 137, 7468 (2015).
L.H. Tjeng, Max Planck Institute for Chemical Physics
X.H. Liu, C.F. Chang, A.D. Rata, A.C. Komarek, and L.H. Tjeng*
Fe3O4 Thin Films: Controlling and Manipulating an Elusive Quantum Material.
Fe3O4 (magnetite) is one of the most studied quantum materials. Numerous studies have been
devoted to describe and to understand its enigmatic Verwey transition, also the first example of a
metal-insulator transition in oxides. Yet, the underlying mechanism remains elusive. Nevertheless,
the theoretically expected half-metallic behavior generates high expectations that magnetite in the
thin film form can be used in spintronic devices such as spin valves, magnetic tunnel junctions, and
so on. A tremendous amount of work has been devoted to preparing thin films with high crystalline
quality. Using a variety of deposition methods, epitaxial growth on a number of substrates has been
achieved. Yet, the physical properties of the thin films are not that well defined as those of the bulk
material. In particular, the first order metal-insulator transition, known as Verwey transition, is in thin
films very broad as compared to that in the bulk single crystal. The Verwey transition temperature
TV in thin films is also much lower, with reported values ranging from 100 to 120 K, while the
stoichiometric bulk has TV of 124–125 K. It is not clear why the Verwey transition in thin films is so
diffuse.
In this work, we investigate systematically the effect of oxygen stoichiometry, thickness, strain,
and microstructure on the Verwey transition in epitaxial Fe3O4 thin films on a variety of substrates.
We use molecular beam epitaxy (MBE) technique under ultrahigh vacuum conditions combined
with in-situ electron diffraction and x-ray spectroscopic characterization as well as ex-situ x-ray
diffraction and electrical conductivity measurements. We have been able to determine the factors
that affect negatively the Verwey transition in thin films and we have succeeded in growing
magnetite thin films which not only have the Verwey transition as sharp as in the bulk, but also
show transition temperatures that are substantially higher than the bulk. The break through is the
realization that we have to search for a class of substrate materials that is particular for magnetite.
We have identified the Co(2-x-y)Mn(x)Fe(y)TiO4 system as the material of choice, and have made
special efforts to grow single crystals of this for the fabrication of the substrates. Using these tailormade substrates and the strain exerted by these substrates, our record of the Verwey transition
temperature so far, which is the world record as well, is 136.5 K, about 12 K higher than that of the
bulk single crystal and about 25 K higher than that of epitaxial thin films so far published. Obviously,
the occurrence of the Verwey transition in the highly anisotropic strained films has raised also a new
question to the intricacies of the interplay between the charge and orbital degrees of freedom of
the Fe ions in magnetite.
*Correspondence should be addressed to [email protected].
Presentations
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A. Tsukazaki, Institute for Materials Research, Tohoku University
High-Tc superconductivity in FeSe electric-double-layer transistor.
Iron selenide (FeSe), one of Fe-based superconductors, exhibits very unique properties where the
superconducting transition temperature (Tc) is largely enhanced under ultrathin condition from
bulk value (Tc ~ 8 K). In particular, the large superconducting gap of about 20 meV, corresponding
to about 65 K, has been detected in one-unit-cell FeSe deposited on SrTiO3 substrates by scanning
tunnel spectroscopy (STS) [1] and angle-resolved photoemission spectroscopy (ARPES) [2,3]. The
origin for the enhancement of Tc is still under debate with such as electron-phonon coupling,
charge doping effect, strain effect, and modulation of band structure. We demonstrate that the
electrochemical etching approach allows us to measure transport properties of ultrathin FeSe films
with systematic manner from thick (over 20 monolayers) to about monolayer. In this talk, we will
present the thickness dependence of superconductivity as well as electrostatic control of electrical
properties [4] for FeSe films grown on various kinds of insulting oxide substrates. In addition, we will
discuss about the experimental schemes of transport measurements on FeSe electric-double-layer
transistor and the origin of the high-Tc superconductivity.
Acknowledgements: This study is partially supported by a Grant-in-Aid for Scientific Research
on Innovative Areas “Topological Materials Science” (KAKENHI Grant No. 15H05853) and “Topo-Q
program” and (KAKENHI Grant No. 25000003) from JSPS of Japan.
References: [1] Q. Y. Wang et al., Chin. Phys. Lett. 29, 037402 (2012). [2] S. He et al., Nat. Mater. 12,
605 (2013). [3] J. J. Lee et al., Nature 515, 245 (2014). [4] J. Shiogai et al., Nature Phys. 12, 42 (2016).
Qi-Kun Xue, Department of Physics, Tsinghua University
Interface engineering of high temperature superconductivity.
[abstract missing]
Peidong Yang, University of California, Berkeley
Semiconductor Nanowires for Energy Conversion.
Semiconductor nanowires, by definition, typically have cross-sectional dimensions that can be
tuned from 2–200 nm, with lengths spanning from hundreds of nanometers to millimeters. After
more than two decades of research, nanowires can now be synthesized and assembled with specific
compositions, heterojunctions and architectures. This has led to a host of nanowire photonic and
electronic devices. Because of their unique structural, chemical and physical properties, these
nanoscopic one-dimensional nanostructures can also play a significant role in terawatt-scale energy
conversion and storage. Currently the amount of energy required worldwide is on the scale of
terawatts, and the percentage of renewable energy in the current energy portfolio is quite limited.
Developing of cost-effective clean energy technology becomes imperative. I will discuss two
examples from my group, approaching this problem in two different directions. The first relates to
saving energy, by developing nanostructured silicon thermoelectrics to do waste heat recovery; and
the second is to develop nanostructures for solar energy conversion, especially converting CO2 to
liquid fuels through artificial photosynthesis.
Han Woong Yeom, Center for Artificial Low Dimensional Electronic System, Institute for Basic
Science; Department of Physics, POSTECH, Pohang University
Creating heterointerfaces with textured electronic states on correlated transition metal
dichalcogenides.
Domain walls and heterointerfaces in magnetic, ferroelectric, and multiferroic materials have
played multiply important roles for various fundamental and technological issues. In this talk, we
will review our recent research activity for domain walls and heterojuctions in correlated transition
metal dichalcogenides of 1T-TaS2 and IrTe2. Domain walls in the charge density wave (CDW)
and Mott insulating state of 1T-TaS2 are thought to be important for metal-insulator transitions,
emerging superconductivity, and ultrafast device applications. We discover a method to manipulate
domain walls in nanoscale [1] creating a unique heterointerface of correlated metal and MottCDW insulator. Two well defined in-gap states are discovered within domain walls [2]. These states
are largely determined by strong electron correlation intrinsic to this material, indicating the
internal degrees of freedom within domain walls. In IrTe2, we discover a new charge ordered state
with a hexagonal order and with superconductivity below 3.1 K. It corresponds to a 3q state of
1q stripe orders and forms a heterointerface of superconducting 3q and normal 1q states at low
temperature. We will introduce how these systems can further be exploited to synthesize interesting
heterointerfaces in vertical direction too by growing epitaxial films on top.
References: [1] D. Cho et al., Nat. Commun. 7, 10453 (2016). [2] D. Cho et al., in preparation. [3] H. S.
Kim et al., Nano Lett. 16, 4260 (2016). [4] H. S. Kim et al., submitted.
Posters
Ken Ahn, Department of Physics, New Jersey Institute of Technology
Theory of K-edge resonant inelastic x-ray scattering and its application to strongly
momentum-dependent screening dynamics in La0.5Sr1.5MnO4.
We present a formula for the calculation of K-edge resonant inelastic x-ray scattering (RIXS) on
transition-metal compounds, based on a local interaction between the valence shell electrons
and the 1s core hole. We apply this formula to a single-layered charge-, orbital-, and spin-ordered
manganite, La0.5Sr1.5MnO4. The comparison between theoretical results and experimental data
shows that the observed strong momentum dependence of the intensity reflects highly localized,
nearest-neighbor screening of the transient local charge perturbation with an exciton-like
screening cloud, which demonstrates the potential of K-edge RIXS as a probe of screening dynamics
in materials.
References: T. F. Seman, X. Liu, J. P. Hill, M. van Veenendaal, K. H. Ahn, Phys. Rev. B 90, 45111 (2014);
X. Liu, T. F. Seman, K. H. Ahn, M. van Veenendaal, D. Casa, D. Prabhakaran, A. T. Boothroyd, H. Ding,
and J. P. Hill, Phys. Rev. B 87 - Rapid Commun., 201103(R) (2013); K. H. Ahn, A. J. Fedro, and M. van
Veenendaal, Phys. Rev. B 79, 045103 (2009).Candle Fragrance Evaluation via qPOD® Technology.
Q Research Solutions, Old Bridge, New Jersey
Elke Arenholz, Advanced Light Source, Lawrence Berkeley National Laboratory and Department of
Materials Science and Engineering, University of California, Berkeley
Understanding nanoscale heterogeneity and phase coexistence in quantum materials.
Heterogeneity of quantum materials on the nanoscale can result from the spontaneous formation
of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence
of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge,
Posters
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orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example,
coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal
magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and
charge-ordered and superconducting regions are present simultaneously in materials exhibiting
high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or
strain) or other external excitations (light or heat) can tip the energy balance towards one phase,
or support heterogeneity and phase coexistence and provide the means to perturb and tailor
quantum heterogeneity at the nanoscale.
Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what
is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively
a method of ‘spray painting’ atoms on single crystalline substrates to create precisely customized
layered structures with atomic arrangements defined by the underlying substrate. Charge transfer
and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between
adjacent layers lead to intriguing and important new phenomena testing our understanding of
basic physics and creating new functionalities. Moreover, the abrupt change of orientation of
an order parameter between nanoscale domains can lead to unique phases that are localized at
domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic
domain walls in antiferromagnets.
Here we present our recent results on tailoring the electronic anisotropy of multiferroic
heterostructures by imprinting the BiFeO3 domain pattern in an adjacent La0.7Sr0.3MnO3 layer
[1], understanding the metal-insulator transition in strained VO2 thin films [2] and identifying a
three-dimensional quasi-long-range electronic supermodulation in YBa2Cu3O7-x/La0.7Ca0.3MnO3
heterostructures [3].
References: [1] C. Ju et al., Adv. Mater. 28, 876 (2016). [2] A.X. Gray et al., Phys. Rev. Lett. 116, 116403
(2016). [3] J. He et al., Nat. Commun. 7, 10852 (2016).
MIng-Wen Chu, Center for Condensed Matter Sciences, National Taiwan University
P. W. Lee1,2, M.-W. Chu2*, V. N. Singh1,3, G. Y. Guo1,4, H.-J. Liu5, J.-C. Lin6, Y.-H. Chu5,6 & C. H. Chen2,7
1
Department of Physics, National Taiwan University, Taipei 106, Taiwan. 2Center for Condensed
Matter Sciences, National Taiwan University, Taipei 106, Taiwan. 3Institute of Atomic and Molecular
Sciences, Academia Sinica, Taipei 106, Taiwan. 4Physics Division, National Center for Theoretical
Sciences, Hsinchu 300, Taiwan. 5Department of Materials Science and Engineering, National Chiao
Tung University, Hsinchu 300, Taiwan. 6Institute of Physics, Academia Sinica, Taipei 105, Taiwan.
7
Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA.
Hidden lattice instabilities: origin of the conductive interface between insulating LaAlO3 and
SrTiO3.
The metallic interface between insulating LaAlO3 and SrTiO3 opens up the field of oxide electronics
and displays order parameters absent in parent bulks such as superconductivity, ferromagnetism,
and sensitivity to electromechanical stimuli like insulating ferroelectrics. With more than a decade
of researches on this model oxide heterostructure, the fundamental origin of the interfacial
conductivity is, by all means, unsettled, let alone why there shall be the collective properties. Here
we resolve this long-standing puzzle of the interfacial metallicity by atomic-scale observation of
electron-gas formation for screening hidden ferroelectric-like lattice instabilities, rejuvenated near
the interface by epitaxial strain. Using atomic-resolution imaging and electron spectroscopy, the
generally-accepted notions of polar catastrophe and cation intermixing for the metallic interface
are discounted. Instead, the conductivity onset at the critical thickness of four unit-cell LaAlO3 on
SrTiO3 substrate is structurally accompanied with head-to-head ferroelectric-like polarizations
across the interface due to strain-rejuvenated ferroelectric-like instabilities in LaAlO3 and SrTiO3. The
divergent depolarization fields of the head-to-head polarizations cast the interface into an electron
reservoir, forming screening electron gas in SrTiO3 with LaAlO3 hosting complementary localized
holes. The ferroelectric-like polarizations and electron-hole juxtaposition reveal the cooperative
nature of metallic LaAlO3 / SrTiO3, shedding new light on the superconducting, ferromagnetic,
and ferroelectric-like subtleties. This strain-hidden-lattice-instabilities interaction provides a new
paradigm for novel physics at oxide interfaces.
*Correspondence should be addressed to [email protected].
Shuai Dong, Department of Physics, Southeast University
Yakui Weng1, Lingfang Lin1, Elbio Dagotto2, 3, Shuai Dong1*
1
Department of Physics, Southeast University, Nanjing, China. 2Department of Physics and
Astronomy, University of Tennessee, Knoxville, USA. 3Materials Science and Technology Division, Oak
Ridge National Laboratory, Oak Ridge, USA.
Inversion of ferrimagnetic magnetization by ferroelectric switching via a novel
magnetoelectric coupling.
Magnetoelectric effects and multiferroic materials are very important both for basic science and
for practical applications [1-2]. Although several multiferroic materials/heterostructures have been
extensively studied, finding strong magnetoelectric couplings for the electric field control of the
magnetization remains challenging. Here, a novel interfacial magnetoelectric coupling (V∙P)(M∙L)
based on three components (ferroelectric dipole P, magnetic moment M, and antiferromagnetic
order L) is analytically formulated. As an extension of carrier-mediated magnetoelectricity, the new
coupling is shown to induce an electric-magnetic hysteresis loop, as shown Fig. 1(e). Realizations
employing BiFeO3 bilayers grown along the [111] axis are proposed, as shown Fig. 1(a-d). Without
involving magnetic phase transitions, the magnetization orientation can be switched by the carrier
modulation driven by the field effect, as confirmed using first-principles calculations [3].
Fig. 1 (a-b) Sketches of G-type AFM order (as in BiFeO3) viewed from different orientations. The
spins are distinguished by colors. (c) Sketch of a superlattice stacking along the pseudo-cubic [111]
direction. (d) The possible orientations of P, with α being the angle between P and the (111) plane.
(e) Sketch of the electric field control of magnetism. The sign of M is turned accompanying the
switch of P, forming an E-M hysteresis loop.
References: [1]. S. Dong, J.-M. Liu, S.-W. Cheong, and Z. Ren, Adv. Phys. 64, 519 (2015). [2]. X. Huang
and S. Dong, Mod. Phys. Lett. B 28, 1430010 (2014). [3]. Y. K. Weng, L. F. Lin, E. Dagotto, and S. Dong,
Phys. Rev. Lett. 117, 037601 (2016).
*Correspondence should be addressed to [email protected].
Posters
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Martha Greenblatt, Rutgers University, Department of Chemistry and Chemical Biology
Designing Polar and Magnetic Oxides in the A2BB’O6-Type Corundum Derivatives.
Polar and magnetic oxides are fundamentally and technically important, but difficult to prepare.
Recently, we were able to synthesize, at high pressure and temperature (HPT) in a Walker-type
multi-anvil cell, a number of new compounds, A2BB’O6 in the corundum-derived and perovskite
structure with unusually small A-site cations.1-5 At HPT the crystal structures of these A2BB’O6 phases
allow the incorporation of strong magnetic transition metal ions on all cation sites for magnetic
and potentially multiferroic, or magnetoelectric behavior and applications in spintronics. Our
aim was to design room-temperature polar ferri- or ferro-magnets by composition modulation of
A2BB’O6 phases. So far, we have successfully prepared a series of polar and magnetic oxides and
systematically investigated the relationship between the crystal, magnetic, and electronic structure
and physical properties. The discovery of polar antiferromagnetic LiNbO3-type (R3c) Mn2FeMO6 (M
= Nb, Ta)1 predicted new polar structures with second-order Jahn-Teller effect ions (such as Nb5+
and Ta5+, d0) at the B’-site and small ions at the A-site of A2BB’O6, which has been confirmed by
the preparation of Zn2FeTaO6.2 In the Ni3TeO6-type (R3) ferrimagnetic semiconductor Mn2FeMoO6
(TC ~ 340 K),3 the polarization of the structure, is found to be stabilized by the spin structure at
high pressure, while at ambient pressure, a new spin structure with lower energy state induces an
unusually low-temperature (~400 - 550 K) cationic rearrangement, which provides a new way to
tune the physical properties at the atomic-scale, under relatively mild conditions, of bulk oxides.
In polar ferrimagnetic Mn2FeWO6 with Ni3TeO6-type structure the charge and size difference
between Fe2+ and W6+ leads to a fully ordered Fe/W lattice and several exotic magnetic phases4.
Other A2BB’O6 compounds with perovskite or distorted perovskite structures and interesting
magnetic properties were also synthesized at HPT, such as Mn2FeReO6 which is half-metallic with
large magnetoresistance and orders ferri-magneticaly at 520 K.5 While all of these materials are
multiferroic, none studied thus far exhibits ferroelectric switching; the search continues.
References: 1. Li, M.-R.; Walker, D.; Retuerto, M.; Sarkar, T.; Hadermann, J.; Stephens, P. W.; Croft,
M.; Ignatov, A.; Grams, C. P.; Hemberger, J.; Nowik, I.; Halasyamani, P. S.; Tran, T. T.; Mukherjee, S.;
Dasgupta, T. S.; Greenblatt, M. Angew. Chem. Int. Ed. 2013, 52, 8406. 2. Li, M.-R.; Stephens, P. W.;
Retuerto, M.; Sarkar, T.; Grams, C. P.; Hemberger, J.; Croft, M. C.; Walker, D.; Greenblatt, M. J. Am.
Chem. Soc. 2014, 136, 8508. 3. Li, M.-R.; Retuerto, M.; Walker, D.; Sarkar, T.; Stephens, P. W.; Mukherjee,
S.; Dasgupta, T. S.; Hodges, J. P.; Croft, M.; Grams, C. P.; Hemberger, J.; Sánchez-Benítez, J.; Huq, A.;
Saouma, F. O.; Jang, J. I.; Greenblatt, M. Angew. Chem. Int. Ed. 2014, 53, 10774. 4. Li, M.-R.; Croft, M.;
Stephens, Peter, W.; Ye, M.; Vanderbilt, D.; Retuerto, M.; Deng, Z.; Grams, Christoph P.; Hemberger,
J.; Hadermann, J.; Li, W.-M.; Jin, C-Q.; Saouma, F. O.; Jang, J. I.; Akamatsu, H., Gopalan, V; Walker, D;
Greenblatt, M. Adv. Mater. 2015, 27, 2177. 5. Man-Rong Li, Maria Retuerto, Zheng Deng, Peter W.
Stephens, Mark C. Croft, Qingzhen Huang, Hui Wu, Xiaoyu Deng, Gabriel Kotliar, Javier SánchezBenítez, Joke Hadermann, David Walker, Martha Greenblatt, Angew. Chem. Int. Ed., 2015, 54, 1.
Myung-Guen Han, Condensed Matter Physics & Materials Science, Brookhaven National Laboratory
Myung-Geun Han1, Joseph A. Garlow1,2, Matthieu Bugnet3, Simon Divilov4, Matthew S. J. Marshall5,6,
Lijun Wu1, Matthew Dawber4, Marivi Fernandez-Serra4, Gianluigi A. Botton3, Sang-Wook Cheong7,
Frederick J. Walker5,6, Charles H. Ahn5,6 and Yimei Zhu1
1
Condensed Matter Physics & Materials Science, Brookhaven National Laboratory, Upton, NY, USA
11953, 2Materials Science & Engineering Department, Stony Brook University, Stony Brook, NY, USA
11794, 3Department of Materials Science and Engineering, McMaster University, Hamilton, ON,
Canada, L8S 4L7, 4Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY,
USA 11794, 5Department of Applied Physics and Center for Research on Interface Structures and
Phenomena, Yale University, New Haven, CT, USA 06520, 6Department of Mechanical Engineering
and Materials Science, Yale University, New Haven, CT, USA 06520, 7Rutgers Center for Emergent
Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, USA 08854.
Coupling between crystallographic shear planes and charged domain walls in oxide
ferroelectric thin films.
Polar discontinuity at interfaces plays deterministic roles in charge transport, magnetism, and even
superconductivity of functional oxides. Most polar discontinuity problems have been explored
in hetero-interfaces between two dissimilar materials, such as LaTiO3/SrTiO3. In this presentation,
we show that charged domain walls (CDWs) in epitaxial thin films of ferroelectric PbZr0.2Ti.0.8O3 are
strongly coupled to polar interfaces by forming ½<101>{h0l} type crystallographic shear planes
(CSPs) [1]. Using aberration-corrected electron microscopy and spectroscopy we illustrate that
the CSPs consist of both conservative and nonconservative segments when coupled to the CDWs,
where compensating charges for the CDWs are provided by vacancies at the CSPs. The CDW/CSP
coupling yields an atomically narrow domain walls, consisting of a single layer of oxygen. This study
shows that the CDW/CSP coupling is a fascinating venue to develop functional material properties.
Acknowledgements: This work was supported by the Materials Science and Engineering Divisions,
Office of Basic Energy Sciences, of the US Department of Energy, under Contract No. DE-AC0298CH10886. TEM sample preparation using FIB was performed at the Center for Functional
Nanomaterials, Brookhaven National Laboratory. The work at Yale University was supported by
NSF MRSEC DMR 119826 (CRISP), DMR 1309868 and FAME. The EELS work was performed at the
Canadian Centre for Electron Microscopy, a national facility supported by the Canada Foundation
for Innovation through the MSI program, NSERC and McMaster University. SWC is funded by the
Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4413 to the Rutgers
Center for Emergent Materials.
References: [1] M.-G. Han, et al., “Coupling of bias-induced crystallographic shear planes with
charged domain walls in ferroelectric oxide thin films”, Phys. Rev. B. (2016) in press.
Rongwei Hu, Rutgers University, Department of Physics and Astronomy
Single crystal growth by laser floating zone method.
The growth of high-quality single crystals is a very exciting prospect and will result in major
discoveries that will change the way we utilize functionalities of crystalline solids in a transformative
manner. The methods to grow high-quality single crystals is therefore highly sought after. We will
demonstrate a few single crystal growths by Laser Floating Zone method (L-FZ), which is recently
developed by Crystal Systems Corporation and discuss the advantages of such method, compared
to the halogen lamp heated Infrared Optical Floating Zone (IR-FZ).
Fei-Ting Huang, Rutgers University, Center for Emergent Materials, Physics and Astronomy
F.-T. Huang1, B. Gao1, J.-W. Kim1, X. Luo2, Y. Wang2, L. H. Wang2 and S.-W. Cheong1,2*
1
Rutgers Center for Emergent Materials, Department of Physics and Astronomy, Rutgers University,
Piscataway, New Jersey 08854, USA. 2 Laboratory for Pohang Emergent Materials and Max Plank
POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology.
Evolution of domain topology in bi-layered perovskites.
Hybrid improper ferroelectricity (HIF) material Ca3-xSrxTi2O7 shows a rich phase diagram over a
broad range of concentrations x, both crystallographically and phenomenally. High quality and
cleavable single crystals have been prepared through floating zone growths and performing x-ray,
TEM, PFM and dielectric measurements on well-characterized samples. The switchable polarization
of 8 µC·cm-2 in bulk crystals at room temperature has been experimentally1 verified in the HIF
orthorhombic states (0≤x≤0.9). Ferroelectricity described by a hybridization of two structural modes
(octahedral tilt X3- and rotation X2+ modes) turns out to be associated with an intriguing domain
topology consisting of Z4×Z2 domains and Z3 vortices with eight domains (4 directional domains
and 2 antiphase domains), abundant charged domain walls and unique zipper-like switching
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kinetics2. When octahedral rotation (thus, HIF) is suppressed by chemical doping/ionic ordering
near the polar-centrosymmetric phase boundary (x~0.93), a new domain topology Z2×Z2 domains
and Z4 vortices (2 directional domains and 2 antiphase domains) emerge in the intermediate
tetragonal state, arising from the active octahedral tilt X3- mode3. We found the presence of plentiful
topological Z4 vortex-antivortex pairs, associated with four oxygen octahedral tilts at domains and
another four different oxygen octahedral tilts at domain walls. The connection between charged
domain walls, topological defects and the macroscopic domain wall connectivity/topology will be
presented. The work at Rutgers was supported by the Gordon and Betty Moore Foundation’s EPiQS
Initiative through Grant GBMF4413 to the Rutgers Center for Emergent Materials.
References: [1] Y. S. Oh, X. Luo, F.-T. Huang, Y. Wang, and S.-W. Cheong, Experimental demonstration
of hybrid improper ferroelectricity and the presence of abundant charged walls in (Ca,Sr)3Ti2O7
crystals, Nat. Mater. 14 (2015) 407–413. [2] F.-T. Huang, F. Xue, B. Gao, L. H. Wang, X. Luo, W. Cai, X.-Z.
Lu, J. M. Rondinelli, L. Q. Chen and S.-W. Cheong, Domain topology and domain switching kinetics
in a hybrid improper ferroelectric, Nat. Commun. 7 (2016) 11602. [3] F.-T. Huang, B. Gao, J.-W. Kim, X.
Luo, Y. Wang, M.-W. Chu, C.-K. Chang, H.-S. Sheu and S.-W. Cheong, Topological defects at octahedral
tilting plethora in bi-layered perovskites, arXiv:1606.01203v2
Jason Kawasaki, University of Wisconsin, Madison
Jason Kawasaki,1 Anderson Janotti,2 and Chris Palmstrom3
1
University of Wisconsin, Madison. 2University of Delaware. 3University of California, Santa Barbara
Observation of a bulk bandgap and metallic surface states in the 18 electron half Heusler
compound CoTiSb.
Gapped half Heusler compounds show great promise for the development of earth abundant
thermoelectrics, half metallic ferromagnets for spin injection, and topological heterostructures.
However, due to the lack of momentum resolved electronic structure measurements, the origins of
the bulk bandgap in these materials remain unclear. Moreover, the surfaces and interfaces, which
are critical to heterostructures, are poorly understood. Here, using the canonical 18 electron half
Heusler CoTiSb, we demonstrate the existence of a bulk bandgap and dispersions in quantitative
agreement with density functional theory calculations, but also metallic surface states. Using a
combination of molecular beam epitaxy, angle resolved and core level photoemission, scanning
tunneling microscopy, and density functional theory, we show that surface states are formed by a
surface reconstruction in CoTiSb that compensates for surface charge via creation of Ti vacancies,
and minimizes Sb dangling bonds through dimer formation. Our studies, which are the first
momentum resolved measurements for any finite gapped Heusler, place design constraints on
Heusler heterostructures, in which parasitic conduction through trivial metallic surface states needs
to be minimized.
Jaewook Kim, Rutgers University, Center for Emergent Materials, Physics and Astronomy
Jaewook Kima, C. J. Wonb, L. Zhangb, A. Admasua, and S.-W. Cheonga,b
a
Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers
University, Piscataway, NJ 08854. bLaboratory for Pohang emergent materials and Department of
Physics, POSTECH, Pohang 790-784, Korea.
Exploration of chemically-controlled transition metal dichalcogenides.
Transition metal chalcogenides has attracted lots of attention because of its plethora of electronic/
structural phases that differ among various compositions and polymorphs. Recently, it has been
demonstrated that external parameters such as chemical-doping, carrier injection, electric field,
pressure, and strain. For example, in 1T-TaS2, gate-controlled intercalation can tune the system from
a charge density wave to superconducting phase in a field-effect transistor configuration [1]. In the
Td phase of WTe2, which is expected to host Weyl semimetal phase [2], a large and non-saturating
magnetoresistance was observed [3]. In this regard, we have successfully grown diverse series of
transition metal dichalcogenides with different doping and studied their physical properties. We
will introduce several examples where structural or electronic phases are controlled by chemical
doping. Examples include, destabilization of the commensurate charge density wave (CDW) in TaS2,
modification of structural transition in MoTe2. We also show that polar structure stabilized in these
systems may show intriguing coexistence of CDW and superconductivity.
References: [1] Y. Yu et al. Nat. Nano. 10, 270 (2015). [2] A. Soluyanov et al. Nature 527, 495 (2015). [3]
M. Ali et al. Nature 514, 205 (2014).
Wei-Li Lee, Institute of Physics, Academia Sinica
Spin‐orbit coupled superconductivity at the interface of LaAlO3/SrTiO3.
By using oxide MBE technique, we have grown few monolayers of epitaxial LaAlO3 (LAO) on TiO2
terminated SrTiO3 (STO) substrates, which shows an interface superconductivity below about 0.3 K.
Scanning tunneling electron microscope images revealed a sharp atomic interface between LAO
and STO in our LAO/STO samples. By fabricating a back gate electrode via the STO substrate, the
superconductor‐insulator transition was observed by applying gate voltages on a macroscopic
size of the two‐dimensional electron liquid (2DEL) at the interface of LAO/STO. From the
uperconducting critical field anisotropy measurements, a sizable spin‐orbit coupling (SOC) is likely
to present in the superconducting phase, where the upper limit of the SOC strength can be largely
tuned by gate voltages. In addition, magneto‐transport anomaly was found when depleting the
electron density and thus driving the 2DEL into insulating phase, suggesting an inhomogeneous
density distribution and also a possible multi‐band conduction in the 2DEL.
Steve J. May, Department of Materials Science and Engineering, Drexel University
A. K. Choquette,1 C. R. Smith,1 R. J. Sichel-Tissot,1,2 E. J. Moon,1 M. D. Scafetta,1 E. Di Gennaro,3 F. Miletto
Granozio,3 and S. J. May1*
1
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104 USA.
2
Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 USA. 3 CNR-SPIN and
Dipartimento di Fisica, Università di Napoli “Federico II”, 80126 Naples, Italy.
Coupling between crystallographic shear planes and charged domain walls in oxide
ferroelectric thin films.
There is growing interest in designing and controlling the rotations of corner-connected BO6
octahedra in ABO3 perovskite heterostructures to induce new functionality in these material
systems. For example, there have been many recent predictions of designing improper
ferroelectrics, polar metals, and multiferroics based on ultrashort period superlattices that exhibit
the a-a-c+ rotation pattern in the orthorhombic (Pbnm) perovskite structural variant. To realize such
predictions, it is necessary to achieve deterministic control over the rotation pattern orientation in
Pbnm films and superlattices. We present a systematic study of how the crystallographic orientation
of the rotation pattern responds to both epitaxial strain and substrate imprinting in a variety of
Pbnm-type heterostructures.[1] Using synchrotron diffraction to measure octahedral rotation
patterns, we show that compressive strain strongly favors a-a-c+ rotation patterns and tensile strain
weakly favors a-a-c+ structures. We also demonstrate that in films grown on orthorhombic substrates,
the orientation of the rotation pattern is imprinted into the film from the substrate even for epitaxial
conditions where strain would favor the opposite structural orientation. The primacy of substrate
imprinting over strain in determining the in-phase rotation axis points to growth on (001)-oriented
Pbnm-type substrates as the most promising means to ensure a-a-c+ behavior in perovskite films and
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superlattices.
Acknowledgements: Work at Drexel was supported by the National Science Foundation (DMR1151649). Use of the Advanced Photon Source was supported by the U. S. Department of Energy,
Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
References: [1] A. K. Choquette, C. R. Smith, R. J. Sichel-Tissot, E. J. Moon, M. D. Scafetta, E. Di
Gennaro, F. Miletto Granozio, E. Karapetrova, and S. J. May, “Octahedral rotation patterns in strained
EuFeO3 and other Pbnm perovskite films: Implications for hybrid improper ferroelectricity”, Physical
Review B 94, 024105 (2016).
*Correspondence should be addressed to [email protected].
Jagadeesh S. Moodera, Physics Department, Francis Bitter Magnet Lab, Plasma Science and Fusion
Center, Massachusetts Institute of Technology
1
Physics Department, 2Francis Bitter Magnet Lab, 3Plasma Science and Fusion Center, M.I.T.
In collaboration with: At MIT, CuiZu Chang,2,3 Ferhat Katmis, 1.2,3 Peng Wei. 1,2,3; At Penn State U,
W-W. Zhao, D. Y. Kim, C-x. Liu, J. K. Jain, M. H. W. Chan; At Oakridge National Lab, V. Lauter; From
Northeastern U., B. A. Assaf, M. E. Jamer, D. Heiman; At Argonne Lab, J. W. Freeland; At Saha Institute
of Nuclear Physics (India), B. Satpati.
Quantum anomalous Hall state and dissipationless chiral conduction in topological insulator
thin films with broken time reversal symmetry.
Most of the exotic quantum phenomena predicted in a topological insulator (TI) needs to have
broken time reversal symmetry (TRS) by ferromagnetic perturbation of their Dirac surface states.
The quantum anomalous Hall (QAH) effect and dissipationless quantized Hall transport are two of
the very important predictions in these systems. Besides growing high quality TI thin films, ideal
magnetic doping and tuning of Fermi to the exchange gap is required. The realization of the QAH
effect in realistic materials requires ferromagnetic insulating materials that have topologically nontrivial electronic band structures. In a TI, the ferromagnetic order and TRS breaking is achievable
through doping with a magnetic element or via ferromagnetic proximity coupling with a
magnetic material. Our both experimental approaches showed excellent results along with some
unanticipated observations: the proximity induced magnetism in TI exhibited stability far above
the expected temperature range. We will discuss the robust QAH state and dissipationless chiral
edge current flow achieved in a hard ferromagnetic TI system. This could be a major step to lead us
towards dissipationless electronic applications, making such devices more amenable for metrology
and spintronics applications. Furthermore, our study of the gate and temperature dependences of
transport measurements may elucidate the causes of the dissipative edge channels and the need
for very low temperature to observe QAH.
Acknowledgements: Work supported by NSF Grant DMR-1207469, the ONR Grant N00014-13-10301, and the STC Center for Integrated Quantum Materials under NSF grant DMR-1231319.
References: 1. P. Wei et al., Phys. Rev. Lett. 110, 186807 (2013). 2. C-Z Chang et al., Nat. Matl. 13, 473
(2015); Phys. Rev. Lett. 115, 057206 (2015). 3. F. Katmis et al., Nature (to be published, May 2016).
William D. Ratcliff, Nistona Oceanic and Atmospheric Administration
William D. Ratcliff⁶, Julia A. Mundy1, Charles M. Brooks2, Megan E. Holtz1, Jarrett A. Moyer3, Hena
Das1, Alejandro F. Rébola1, John T. Heron2,⁴, James D. Clarkson⁵, Steven M. Disseler⁶, Zhiqi Liu⁵, Alan
Farhan⁷, Rainer Held2, Robert Hovden1, Elliot Padgett1, Qingyun Mao1, Hanjong Paik2, Rajiv Misra⁸,
Lena F. Kourkoutis1,9, Elke Arenholz⁷, Andreas Scholl⁷, Julie A. Borchers⁶, , Ramamoorthy Ramesh⁵,10,11,
Craig J. Fennie1, Peter Schiffer3, David A. Muller1,9 & Darrell G. Schlom2,9
1School of Applied and Engineering Physics, Cornell University; 2Department of Materials Science
and Engineering, Cornell University; 3Department of Physics and Frederick Seitz Materials Research
Laboratory, University of Illinois at Urbana-Champaign; 4Department of Materials Science and
Engineering, University of Michigan; ⁵Department of Materials Science and Engineering, University
of California, Berkeley; ⁶NIST Center for Neutron Research, National Institute of Standards and
Technology; ⁷Advanced Light Source, Lawrence Berkeley National Laboratory; ⁸Department
of Physics, Pennsylvania State University; ⁹Kavli Institute at Cornell for Nanoscale Science;
10Department of Physics, University of California, Berkeley; 11Materials Sciences Division, Lawrence
Berkeley National Laboratory.
Engineering a Room-Temperature Magnetoelectric Multiferroic.
In this poster, we present recent results in LuFeO3/LuFe2O4 superlattices. We achieve an enhanced
magnetic transition temperature of 281 K. The presence of ferroelectric LuFeO3 drives LuFe2O4
into a ferroelectric state and we observe strong magnetoelectric coupling at 200 K. The design
principles used here offer an alternative approach to realizing functional multiferroic devices.
Maryam Salehi, Rutgers University, Materials Science and Engineering
Maryam Salehi1, Nikesh Koirala2, Jisoo Moon2, Deepti Jain2, Pavel Shibayev2 and Seongshik Oh2
1Materials Science and Engineering, Rutgers University; 2Department of Physics and Astronomy,
Rutgers University.
Interface-engineered topological insulator thin films with quantum and finite size effect.
Topological insulators (TIs) are novel class of quantum materials where the bulk remains insulating,
while the surface is metallic. These topological surface states (TSS) exhibit linear Dirac-like
dispersion. Bi2Se3 is a prototypical 3D topological insulator with relatively large band gap of 0.3eV
and has a single TSS with Dirac cone well separated from bulk band edges, making it an ideal
material to study the novel physics of TSS. Due to its layered structure, Bi2Se3 thin films can be
grown with ease using molecular beam epitaxy (MBE) on variety of substrates. However, all of the
so far grown thin films suffer from high sheet carrier density nsheet (~ 1013-1014/cm2) and low
carrier mobility μ (~ 2000 cm2/Vs), mostly due to defects induced by substrate. With advanced
heteroepitaxy engineering we have achieved TI thin films of Bi2Se3 that are free of bulk conduction
with an order of lower sheet carrier density (~1 to 4 ×1012/cm2) while maintaining the record high
carrier mobility μ (up to ~16,000 cm2/Vs). In this poster, the growth procedure and the properties of
these new generation samples will be presented. We will also show how these interface-engineered
samples combined with proper capping layer revealed previously hidden aspects of topological
insulators, such as the first-time observation of TSS-originated quantum Hall effect, quantized
Faraday and Kerr rotation, and finite-size driven topological phase transition.
Trevor A. Tyson, Department of Physics, New Jersey Institute of Technology
Han Zhang1, Tian Yu1, Sizhan Liu1, Mark Croft2, Megan E. Scofield3, Stanislaus S. Wong3,4 and
Trevor A. Tyson1
1Department of Physics, New Jersey Institute of Technology; 2Department of Physics and Astronomy,
Rutgers University; 3Department of Chemistry, State University of New York at Stony Brook;
⁴Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory.
Polar State and Phase Diagram of Freestanding Strontium Titanate Nanoparticles.
Monodispersed strontium titanate nanoparticles were prepared and studied in detail [1]. It is found
that ~10 nm as-prepared stoichiometric nanoparticles are in a polar structural state (with possibly
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ferroelectric properties) over a broad temperature range. A tetragonal structure, with possible
reduction of the electronic hybridization is found as the particle size is reduced. In the 10 nm
particles, no change in the local Ti-off centering is seen between 20 and 300 K. Pressure-dependent
structural measurements of various monodisperse nanoscale STO samples with average diameters
of 10 nm, 20 nm, 40 nm, and 83 nm at pressures of up to 13 GPa were also conducted. For the
systems above 10 nm, a structural phase transition was observed at a pressure (Pc) which decreases
with decreasing particle size. On the other hand, robust pressure independent polar structure was
detected in the 10 nm sample for pressures of up to 13 GPa. The results suggest that the growth of
~10 nm STO particles on an underlying substrate, which does not necessarily match to the overlaid
STO lattice, will not alter the polar state of the system for a large range of strain values, thereby
possibly enabling more widespread device use. This indicate that nanoscale motifs of SrTiO3 may be
utilized in data storage as assembled nano-particle arrays in applications where, pressure stability,
chemical stability, temperature stability and low toxicity are critical issues.
Acknowledgements: This work is supported by U.S. DOE Grant DE-FG02-07ER46402.
References: [1] (a) Zhang et al., unpublished and (b) Tyson et al. Appl. Phys. Lett. 105, 091901 (2014).
Valery Kiryukhin, Rutgers University, Department of Physics and Astronomy
Magnetic properties of non-centrosymmetric functional compounds.
Materials combining non-centrosymmetric crystalline structure with magnetism, either in the form
of static magnetic order, or in spin-polarized electronic bands, were recently found to exhibit novel
functional properties. In this poster, we discuss three examples: (1) giant magnetoelectricity in polar
magnet Fe2Mo3O8, (2) switchable magnetic polarization of the electronic bands in nonmagnetic
metal IrTe2, and (3) unusual spin waves in a langasite compound with structural chirality.
Wenbo Wang, Department of Physics and Astronomy, Rutgers University
Wenbo Wang1, Cui-Zu Chang2, Jagadeesh S. Moodera2,3,and Weida Wu1
1Department of Physics and Astronomy, Rutgers University; 2Francis Bitter Magnet Lab, Massachusetts
Institute of Technology; 3Department of Physics, Massachusetts Institute of Technology.
Visualizing ferromagnetic domain behavior of magnetic topological insulator thin films.
The breaking of time reversal symmetry in a topological insulator (TI) can lead to exotic quantum
effects, such as magnetic monopoles, quantum anomalous Hall effect (QAHE), and so on. QAHE
was first experimentally observed in a ferromagnetic topological insulator Cr doped BixSb2-xTe3[1].
Recently, a more robust quantum anomalous Hall state has been observed in V doped BixSb2-xTe3
thin film, which has a larger coercive field and higher Curie temperature[2]. Here we present a
systematic magnetic force microscopy (MFM) study of domain behaviors in thin films of the magnetic
topological insulator Sb1.89V0.11Te3. Our MFM results reveal that in the virgin domain state, after zerofield cooling, an equal population of up and down domains occurs. Interestingly, the cooling field
dependence of MFM images demonstrates that small cooling magnetic field (~5-10 Oe) is sufficient
to significantly polarize the film despite the coercive field (Hc) for these films being on the order of a
tesla. By visualizing the magnetization reversal process around HC of V-doped Sb2Te3, we observed a
typical domain behavior of a ferromagnet, i.e. Domain nucleation and domain wall propagation. Our
results provide direct evidence of ferromagnetic behavior of the magnetic topological insulator, a
necessary condition for robust anomalous Hall effect.
Acknowledgements: This work is supported by DOE BES under award # DE-SC0008147.
References: [1] C.-Z. Chang et al., Science 340, 167 (2013). [2] C.-Z. Chang et al., Nature Materials 14,
473–477(2015).
Weida Wu, Department of Physics and Astronomy, Rutgers University
Wenhan Zhang, Maryam Salehi, Seongshik Oh, and Weida Wu
Restoring Pristine Surface of Topological Insulator Thin Films with Effective Se/Te Decapping
Processes.
High quality thin films of topological insulators (TI) such as Bi2Se3 and Sb2Te3 have been successfully
synthesized by molecular beam epitaxy (MBE). Although the surface of MBE films can be protected
by capping with inert materials such as amorphous Se or Te, restoring an atomically clean pristine
surface after decapping has never been demonstrated, which prevents in-depth investigations of
the intrinsic properties of TI thin films with ex-situ tools. Using high resolution scanning tunneling
microscopy/spectroscopy (STM/STS), we demonstrate a simple and highly reproducible Se
decapping method that allows recovery of the pristine surface of extremely high quality Bi2Se3
thin films transferred from a separate MBE system[1]. The crucial step of our decapping process is
the removal of the surface contaminants on top of amorphous Se before thermal desorption of Se
at a mild temperature (~210 °C). Similar decapping recipe was also demonstrated for Te capping
on Sb2Te3 thin films. The effective Se/Te decapping process opens up the possibility of ex-situ
characterizations of pristine surfaces of interesting chalcogenide or other 2D materials and beyond
using cutting-edge techniques.
References: [1] Jixia Dai, Wenbo Wang, Matthew Brahlek, Nikesh Koirala, Maryam Salehi, Seongshik
Oh and Weida Wu, “Restoring pristine Bi2Se3 surface with an effective Se decapping process”, Nano
Research, 8, 1222-1228 (2014).
Meng Ye, Department of Physics and Astronomy, Rutgers University
Ferroelectricity in corundum derivatives.
The search and discovery of new ferroelectric (FE) materials can broad our understanding of
FE mechanisms and extend the application of FE materials. Corundum derivatives are a class
of material with chemical formula ABO3 or A2BB’O6 in corundum structure. A few corundum
derivatives, e.g. LiNbO3, are FE. Recently, many polar corundum derivatives have been synthesized
under high pressure in laboratory. There are four different structural types for corundum derivatives
and the combinations of cations are enormous. However, the condition under which the structure
can be FE is not clear. In this work, I will introduce the first-principles method to study the coherent
FE barrier, and more realistically the domain wall switching barrier for corundum derivatives. The
method is applied to several polar corundum derivatives and a few new FE materials are predicted.
We also discuss the condition under which the FE structure is compatible with a magnetic ordering.
In addition, we summarize several empirical rules that are correlated with the barrier energy. These
results can greatly accelerate the experimental discovery.
Michael Odell Yokosuk, University of Tennessee
Michael Odell Yokosuk, Amal al-Wahish, Sergey Artyukhin, Kenneth O’Neal, Dipanjan Mazumdar,
Peng Chen, Junjie Yang, Yoon Seok Oh, Stephen A. McGill, Kristjan Haule, Sang-Wook Cheong, David
Vanderbilt, and Janice L. Musfeldt
Magnetoelectric coupling through the spin flop transition in Ni3TeO6.
We combined high field optical spectroscopy and first principles calculations to analyze the
electronic structure of Ni3TeO6 across the 53 K and 9 T magnetic transitions, both of which are
accompanied by large changes in electric polarization. The color properties are sensitive to
magnetic order due to field-induced changes in the crystal field environment, with those around
Ni1 and Ni2 most affected. These findings advance the understanding of magnetoelectric coupling
in materials in which magnetic 3d centers coexist with non-magnetic heavy chalcogenide cations.
Attendees
Peter Abbamonte, University of Illinois, [email protected]
Charles Ahn Ph.D., Yale University, [email protected]
Ken Ahn, New Jersey Institute of Technology, Physics Department, [email protected]
James Analytis, University of California, Berkeley, [email protected]
Elke Arenholz, Lawrence Berkeley National Laboratory, [email protected]
Philip Batson, Rutgers University IAMDN, [email protected]
Ivan Bozovic, Brookhaven National Laboratory, [email protected]
Matthew Brahlek, Penn State University, [email protected]
Yanwei Cao, University of Arkansas, [email protected]
Robert Cava Ph.D., Princeton University, [email protected]
Judy Cha, Yale University, [email protected]
Jak Chakhalian, Rutgers University, Physics and Astronomy, [email protected]
Po-Yao Chang, Rutgers University, Physics and Astronomy, [email protected]
Joseph Checkelsky, Massachusetts Institute of Technology, [email protected]
Yong Chen, Purdue University, [email protected]
Sang-Wook Cheong, Rutgers University, Physics and Astronomy, [email protected]
Manish Chhowalla, Rutgers University, School of Engineering, [email protected]
Ming-Wen Chu, National Taiwan University, [email protected]
Mark Croft, Rutgers University, Physics and Astronomy, [email protected]
Yi Cui, Stanford University, [email protected]
Hong Ding, Institute Of Physics, Chinese Academy Of Sciences, [email protected]
Shuai Dong, Southeast University, [email protected]
Chang-Beom Eom, University of Wisconsin - Madison, [email protected]
Mikhail Eremets, Max Planck Institute for Chemistry, [email protected]
Leonard Feldman, Rutgers University IAMDN, [email protected]
Claudia Felser, Max Planck Institute For Chemical Physics Of Solids, [email protected]
Luke Fleet, Nature Physics, [email protected]
John Freeland, Argonne National Laboratory, [email protected]
Gregory Gabadadze, New York University, [email protected]
Nuh Gedik, Massachusetts Institute of Technology, [email protected]
Matthias Graf, U.S. Department Of Energy, [email protected]
Martha Greenblatt, Rutgers University, Chemistry/Chemical Biology, [email protected]
Jiandong Guo, Institute of Physics, Chinese Academy of Sciences, [email protected]
Myung-Geun Han, Brookhaven National Laboratory, [email protected]
Ke He, Tsinghua University, [email protected]
Honyung Lee, Oak Ridge National Laboratory, [email protected]
Yew San Hor, Missouri University of Science & Technology, [email protected]
Rongwei Hu, Rutgers University, Physics and Astronomy, [email protected]
Fei-Ting Huang, Rutgers University, Physics and Astronomy, [email protected]
Harold Hwang, Stanford University, [email protected]
Sergei Kalinin, The Institute for Functional Imaging of Materials, [email protected]
Jason Kawsaki, University Of Wisconsin-Madison, [email protected]
Andrew Kent, New York University, [email protected]
Jaewook Kim, Rutgers University, Physics and Astronomy, [email protected]
Valery Kiryukhin, Rutgers University, Physics and Astronomy, [email protected]
Gertjan Koster, University of Twente, [email protected]
Irena Kotikova, Gordon and Betty Moore Foundation, [email protected]
Michele Kotiuga, Rutgers University, Physics and Astronomy, [email protected]
Maureen Joel Lagos, Rutgers University IAMDN, [email protected]
Ho Nyung Lee, Oak Ridge National Laboratory, [email protected]
Wei-Li Lee, Institute of Physics, Academia Sinica, [email protected]
Young Hee Lee, Sungkyunkwan University, [email protected]
Jun-Ming Liu, Nanjing University, [email protected]
Xiaoran Liu, University of Arkansas, [email protected]
Yoshiteru Maeno, Kyoto University, [email protected]
Antoine Maignan, Laboratoire CRISMAT CNRS/ENSICAEN/UCBN, [email protected]
David Mandrus, University of Tennessee, [email protected]
Jochen Mannhart, Max-Planck Institute for Solid State Research, [email protected]
Steven May, Drexel University, [email protected]
Lin Miao, New York University, [email protected]
Andrew Millis, Columbia University, [email protected]
John Mitchell, Argonne National Laboratory, [email protected]
Samindranath Mitra, Physical Review Letters, American Physical Society, [email protected]
Tsotomu Miyasaka, Toin University of Yokohama, [email protected]
Jagadeesh Moodera, Massachusetts Institute of Technology, [email protected]
Jisoo Moon, Rutgers University, Physics and Astronomy, [email protected]
Emilia Morosan, Rice University, [email protected]
Margaret Murnane, Joint Institute Lab Astrophysics, [email protected]
Janice Musfeldt, University Of Tennessee, [email protected]
Shuji Nakamura, University of California, Santa Barbara, [email protected]
Taewon Noh, Institute for Basic Science, Seoul National University, [email protected]
Seongshik Oh, Rutgers University, Physics and Astronomy, [email protected]
Johnpierre Paglione, University of Maryland, [email protected]
Stuart Parkin, Max Planck Institute of Microstructure Physics, [email protected]
Dusan Pejakovic, Gordon and Betty Moore Foundation, [email protected]
Jason Petta, Princeton University, [email protected]
Karin Rabe, Rutgers University, Physics and Astronomy, [email protected]
Ramamoorthy Ramesh, University of California, Berkeley, [email protected]
Attendees
(CONTINUED)
William Ratliff II, Nistona Oceanic and Atmospheric Administration, [email protected]
Matthew Rosseinsky, University of Liverpool, [email protected]
Maryam Salehi, Physics and Astronomy, [email protected]
John Schlueter, National Science Foundation, [email protected]
Darrell Scholm, Cornell University, [email protected]
Javad Shabani, City College of New York, [email protected]
Jian Shen, Fudan University, [email protected]
Yuichi Shimakawa, Kyoto University, [email protected]
Peter Sobel, Rutgers University Foundation, [email protected]
Ilya Sochnikov, University of Connecticut, [email protected]
Pappannan Thiyagarajan, U.S. Department of Energy, [email protected]
Liu Hao Tjeng, Max-Planck Institute for Chemical Physics of Solids, [email protected]
Atsushi Tsukazaki, Institute Materials Research, Tohoku University, [email protected]
Trevor Tyson, New Jersey Institute of Technology, Physics Department, [email protected]
David Vanderbilt, Rutgers University, Physics and Astronomy, [email protected]
Wenbo Wang, Rutgers University, Physics and Astronomy, [email protected]
L. Andrew Wray, New York University, [email protected]
Weida Wu, Rutgers University, Physics and Astronomy, [email protected]
Qi-Kun Xue, Tsinghua University, Physics Department, [email protected]
Peidong Yang, University of California, Berkeley, [email protected]
Meng Ye, Rutgers University, Physics and Astronomy, [email protected]
Han Woong Yeom, Pohang University of Science and Technology, [email protected]
Michael Yokosuk, University of Tennessee, [email protected]
Lei Zhang, Penn State University, [email protected]
Notes
Notes
(CONTINUED)
From
Edison
Lightbulb
to LED
Lighting
A Public Lecture with Shuji Nakamura,
2014 Nobel Laureate in Physics
A series of breakthroughs over decades has paved the
way for the emergence of LED light bulbs, and their
ability to reduce the world’s electricity consumption.
Shuji Nakamura shared the Nobel Prize in Physics for
the invention of efficient blue light-emitting diodes
that have enabled energy-saving light sources. Come
hear this world-renowned scholar discuss the past,
present, and future of lighting.
Free and open to the public
Hosted by
The Department of Physics and Astronomy
Monday, August 29, 2016
George Street Playhouse
9 Livingston Avenue
New Brunswick, NJ 08901
Exhibits: 6:30 p.m.
Lecture and Q&A: 7:00 p.m.
Reception: 8:00 p.m.