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Publications

Domain-Dependent Surface Adhesion in Twisted Few-Layer Graphene: Platform for Moiré-Assisted Chemistry

Cornell Affiliated Author(s)
Author
V. Hsieh
D. Halbertal
N.R. Finney
Z. Zhu
E. Gerber
M. Pizzochero
E. Kucukbenli
G.R. Schleder
M. Angeli
K. Watanabe
T. Taniguchi
Eun-Ah Kim
E. Kaxiras
J. Hone
C.R. Dean
D.N. Basov
Abstract

Twisted van der Waals multilayers are widely regarded as a rich platform to access novel electronic phases thanks to the multiple degrees of freedom available for controlling their electronic and chemical properties. Here, we propose that the stacking domains that form naturally due to the relative twist between successive layers act as an additional ”knob” for controlling the behavior of these systems and report the emergence and engineering of stacking domain-dependent surface chemistry in twisted few-layer graphene.

Journal
Nano Letters
Date Published
Group (Lab)

Structural evolution of the kagome superconductors A V3Sb5 (A = K, Rb, and Cs) through charge density wave order

Cornell Affiliated Author(s)
Author
L. Kautzsch
B.R. Ortiz
K. Mallayya
J. Plumb
G. Pokharel
J.P.C. Ruff
Z. Islam
Eun-Ah Kim
R. Seshadri
S.D. Wilson
Abstract

The kagome superconductors KV3Sb5, RbV3Sb5, and CsV3Sb5 are known to display charge density wave (CDW) order which impacts the topological characteristics of their electronic structure. Details of their structural ground states and how they evolve with temperature are revealed here using single crystal x-ray crystallographic refinements as a function of temperature, carried out with synchrotron radiation. The compounds KV3Sb5 and RbV3Sb5 present 2×2×2 superstructures in the Fmmm space group with a staggered trihexagonal deformation of vanadium layers.

Journal
Physical Review Materials
Date Published
Group (Lab)

Melting of generalized Wigner crystals in transition metal dichalcogenide heterobilayer Moiré systems (Nature Communications, (2022), 13, 1, (7098), 10.1038/s41467-022-34683-x)

Cornell Affiliated Author(s)
Author
M. Matty
Eun-Ah Kim
Abstract

The original version of this Article contained an error in the Acknowledgements, which incorrectly read ‘The authors acknowledge support by the NSF [Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM)] under cooperative agreement no. DMR-U638986.’. The correct version states ‘DMR-1539918’ in place of ‘DMRU638986’. This has been corrected in both the PDF and HTML versions of the Article. © The Author(s) 2023.

Journal
Nature Communications
Date Published
Group (Lab)

Machine learning discovery of new phases in programmable quantum simulator snapshots

Cornell Affiliated Author(s)
Author
C. Miles
R. Samajdar
S. Ebadi
T.T. Wang
H. Pichler
S. Sachdev
M.D. Lukin
M. Greiner
K.Q. Weinberger
Eun-Ah Kim
Abstract

Machine learning has recently emerged as a promising approach for studying complex phenomena characterized by rich datasets. In particular, data-centric approaches lead to the possibility of automatically discovering structures in experimental datasets that manual inspection may miss. Here, we introduce an interpretable unsupervised-supervised hybrid machine learning approach, the hybrid-correlation convolutional neural network (hybrid-CCNN), and apply it to experimental data generated using a programmable quantum simulator based on Rydberg atom arrays.

Journal
Physical Review Research
Date Published
Group (Lab)

Melting of generalized Wigner crystals in transition metal dichalcogenide heterobilayer Moiré systems

Cornell Affiliated Author(s)
Author
M. Matty
Eun-Ah Kim
Abstract

Moiré superlattice systems such as transition metal dichalcogenide heterobilayers have garnered significant recent interest due to their promising utility as tunable solid state simulators. Recent experiments on a WSe2/WS2 heterobilayer detected incompressible charge ordered states that one can view as generalized Wigner crystals. The tunability of the transition metal dichalcogenide heterobilayer Moiré system presents an opportunity to study the rich set of possible phases upon melting these charge-ordered states.

Journal
Nature Communications
Date Published
Group (Lab)

Fractional correlated insulating states at one-third filled magic angle twisted bilayer graphene

Cornell Affiliated Author(s)
Author
K. Zhang
Y. Zhang
L. Fu
Eun-Ah Kim
Abstract

The observation of superconductivity and correlated insulating states in twisted bilayer graphene has motivated much theoretical progress at integer fillings. However, little attention has been given to fractional fillings. Here we show that the three-peak structure of Wannier orbitals, dictated by the symmetry and topology of flat bands, facilitates the emergence of a state we name a “fractional correlated insulator” at commensurate fractional filling of ν = n ± 1/3.

Journal
Communications Physics
Date Published
Group (Lab)

Hamiltonian reconstruction as metric for variational studies

Cornell Affiliated Author(s)
Author
K. Zhang
S. Lederer
K. Choo
T. Neupert
Giuseppe Carleo
Eun-Ah Kim
Abstract

Variational approaches are among the most powerful techniques to approximately solve quantum many-body problems. These encompass both variational states based on tensor or neural networks, and parameterized quantum circuits in variational quantum eigensolvers. However, self-consistent evaluation of the quality of variational wavefunctions is a notoriously hard task. Using a recently developed Hamiltonian reconstruction method, we propose a multi-faceted approach to evaluating the quality of neural-network based wavefunctions.

Journal
SciPost Physics
Date Published
Group (Lab)

Harnessing interpretable and unsupervised machine learning to address big data from modern X-ray diffraction

Author
J. Venderley
K. Mallayya
M. Matty
M. Krogstad
J. Ruff
G. Pleiss
V. Kishore
D. Mandrus
D. Phelan
L. Poudel
A.G. Wilson
K. Weinberger
P. Upreti
M. Norman
S. Rosenkranz
R. Osborn
Eun-Ah Kim
Abstract

The information content of crystalline materials becomes astronomical when collective electronic behavior and their fluctuations are taken into account. In the past decade, improvements in source brightness and detector technology atmodern X-ray facilities have allowed a dramatically increased fraction of this information to be captured. Now, the primary challenge is to understand and discover scientific principles from big datasets when a comprehensive analysis is beyond human reach.

Journal
Proceedings of the National Academy of Sciences of the United States of America
Date Published
Group (Lab)

Quantum Phases of Transition Metal Dichalcogenide Moiré Systems

Cornell Affiliated Author(s)
Author
Y. Zhou
D.N. Sheng
Eun-Ah Kim
Abstract

Moiré systems provide a rich platform for studies of strong correlation physics. Recent experiments on heterobilayer transition metal dichalcogenide Moiré systems are exciting in that they manifest a relatively simple model system of an extended Hubbard model on a triangular lattice. Inspired by the prospect of the hetero-transition metal dichalcogenide Moiré system's potential as a solid-state-based quantum simulator, we explore the extended Hubbard model on the triangular lattice using the density matrix renormalization group.

Journal
Physical Review Letters
Date Published
Group (Lab)

Strong interlayer interactions in bilayer and trilayer moire superlattices

Author
S. Xie
B.D. Faeth
Y. Tang
L. Li
E. Gerber
C.T. Parzyck
Debanjan Chowdhury
Y.-H. Zhang
C. Jozwiak
A. Bostwick
E. Rotenberg
Eun-Ah Kim
J. Shan
K.F. Mak
K.M. Shen
Abstract

Moire superlattices constructed from transition metal dichalcogenides have demonstrated a series of emergent phenomena, including moire excitons, flat bands, and correlated insulating states. All of these phenomena depend crucially on the presence of strong moire potentials, yet the properties of these moire potentials, and the mechanisms by which they can be generated, remain largely open questions. Here, we use angle-resolved photoemission spectroscopy with submicron spatial resolution to investigate an aligned WS2/WSe2moire superlattice and graphene/WS2/WSe2trilayer heterostructure.

Journal
Science Advances
Date Published
Group (Lab)
Debanjan Chowdhury Group
Jie Shan Group
Kin Fai Mak Group
Kyle Shen Group