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Publications

Evidence of the fractional quantum spin Hall effect in moiré MoTe2

Cornell Affiliated Author(s)
Author
Kaifei Kang
Bowen Shen
Yichen Qiu
Yihang Zeng
Zhengchao Xia
Kenji Watanabe
Takashi Taniguchi
Jie Shan
Kin Mak
Abstract

Quantum spin Hall (QSH) insulators are two-dimensional electronic materials that have a bulk band gap like an ordinary insulator but have topologically protected pairs of edge modes of opposite chiralities. To date, experimental studies have found only integer QSH insulators with counter-propagating up-spins and down-spins at each edge leading to a quantized conductance G0=e^2/h. Here we report transport evidence of a fractional QSH insulator in 2.1-degree-twisted bilayer MoTe2, which supports spin-Sz conservation and flat spin-contrasting Chern bands.

Journal
Nature
Date Published
Funding Source
DE-SC0019481
FA9550-20-1-0219
DMR-1719875
GBMF11563
NNCI-2025233
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Minimal Fractional Topological Insulator in half-filled conjugate moiré Chern bands

Cornell Affiliated Author(s)
Author
Chao-Ming Jian
Cenke Xu
Abstract

We propose a "minimal" fractional topological insulator (mFTI), motivated by the recent experimental report on the signatures of FTI at total filling factor νtot=3 in a transition metal dichalcogenide (TMD) moiré system. The observed FTI at νtot=3 is likely given by a topological state living in a pair of half-filled conjugate Chern bands with Chern numbers C=±1 on top of another pair of fully-filled conjugate Chern bands. We propose the mFTI as a strong candidate topological state in the half-filled conjugate Chern bands.

Journal
arXiv e-prints
Date Published
Group (Lab)
Chao-Ming Jian Group

Observation of spin polarons in a frustrated moiré Hubbard system

Cornell Affiliated Author(s)
Author
Zui Tao
Wenjin Zhao
Bowen Shen
Tingxin Li
Patrick Knüppel
Kenji Watanabe
Takashi Taniguchi
Jie Shan
Kin Mak
Abstract

The electron’s kinetic energy plays a pivotal role in magnetism. While virtual electron hopping promotes antiferromagnetism in an insulator, real hopping processes usually favour ferromagnetism. However, in kinetically frustrated systems such as hole-doped triangular lattice Mott insulators, real hopping has instead been shown to favour antiferromagnetism. Kinetic frustration has also been predicted to induce a new quasiparticle, a bound state of the doped hole and a spin flip called a spin polaron, at intermediate magnetic fields, which could form an unusual metallic state.

Journal
Nature Physics
Date Published
Funding Source
FA9550-19-1-0390
DE-SC0019481
DMR-1807810
JPMJCR15F3
NNCI-2025233
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Quantum Many-Body Physics Calculations with Large Language Models

Cornell Affiliated Author(s)
Author
Haining Pan
Nayantara Mudur
Will Taranto
Maria Tikhanovskaya
Subhashini Venugopalan
Yasaman Bahri
Michael Brenner
Eun-Ah Kim
Abstract

Large language models (LLMs) have demonstrated an unprecedented ability to perform complex tasks in multiple domains, including mathematical and scientific reasoning. We demonstrate that with carefully designed prompts, LLMs can accurately carry out key calculations in research papers in theoretical physics. We focus on a broadly used approximation method in quantum physics: the Hartree-Fock method, requiring an analytic multi-step calculation deriving approximate Hamiltonian and corresponding self-consistency equations.

Journal
arXiv e-prints
Date Published
Group (Lab)

Γ-VAE: Curvature regularized variational autoencoders for uncovering emergent low dimensional geometric structure in high dimensional data

Cornell Affiliated Author(s)
Author
Jason Kim
Nicolas Perrin-Gilbert
Erkan Narmanli
Paul Klein
Christopher Myers
Itai Cohen
Joshua Waterfall
James Sethna
Abstract

Natural systems with emergent behaviors often organize along low-dimensional subsets of high-dimensional spaces. For example, despite the tens of thousands of genes in the human genome, the principled study of genomics is fruitful because biological processes rely on coordinated organization that results in lower dimensional phenotypes. To uncover this organization, many nonlinear dimensionality reduction techniques have successfully embedded high-dimensional data into low-dimensional spaces by preserving local similarities between data points.

Journal
arXiv e-prints
Date Published
Group (Lab)
Itai Cohen Group
James Sethna Group

Cross Layer Design for the Predictive Assessment of Technology-Enabled Architectures

Cornell Affiliated Author(s)
Author
M. Niemier
X. Hu
L. Liu
M. Sharifi
I. O’Connor
D. Atienza
G. Ansaloni
C. Li
A. Khan
D. Ralph
Abstract

There is great interest in “end-to-end” analysis that captures how innovation at the materials, device, and/or archi-tectural levels will impact figures of merit at the application-level. However, there are numerous combinations of devices and architectures to study, and we must establish systematic ways to accurately explore and cull a vast design space. We aim to capture how innovations at the materials/device-level may ultimately impact figures of merit associated with both existing and emerging technologies that may be employed for either logic and/or memory.

Conference Name
2023 Design, Automation & Test in Europe Conference & Exhibition (DATE)
Date Published

An algorithm for subtraction of doublet emission lines in angle-resolved photoemission spectroscopy

Cornell Affiliated Author(s)
Author
Y. Tarn
M. Sinha
C. Pasco
D.G. Schlom
T.M. McQueen
K.M. Shen
B.D. Faeth
Abstract

Plasma discharge lamps are widely utilized in the practice of angle-resolved photoemission spectroscopy (ARPES) experiments as narrow-linewidth ultraviolet photon sources. However, many emission lines such as Ar-I, Ne-I, and Ne-II have closely spaced doublet emission lines, which result in superimposed replica on the measured ARPES spectra. Here, we present a simple method for subtracting the contribution of these doublet emission lines from photoemission spectra.

Journal
Journal of Electron Spectroscopy and Related Phenomena
Date Published
Funding Source
2039380
Group (Lab)
Kyle Shen Group

Giant spin Hall effect in AB-stacked MoTe2/WSe2 bilayers

Cornell Affiliated Author(s)
Author
Z. Tao
B. Shen
W. Zhao
N.C. Hu
T. Li
S. Jiang
L. Li
K. Watanabe
T. Taniguchi
A.H. MacDonald
J. Shan
K.F. Mak
Abstract

The spin Hall effect (SHE), in which an electrical current generates a transverse spin current, plays an important role in spintronics for the generation and manipulation of spin-polarized electrons. The phenomenon originates from spin–orbit coupling. In general, stronger spin–orbit coupling favours larger SHEs but shorter spin relaxation times and diffusion lengths. However, correlated magnetic materials often do not support large SHEs.

Journal
Nature Nanotechnology
Date Published
Funding Source
DMR-1719875
DMR-1807810
DMR-2039380
FA9550-19-1-0390
NNCI-2025233
DE-SC0019481
JPMJCR15F3
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Remote imprinting of moiré lattices

Author
J. Gu
J. Zhu
P. Knuppel
K. Watanabe
T. Taniguchi
J. Shan
K.F. Mak
Abstract

Two-dimensional moiré materials are formed by overlaying two layered crystals with small differences in orientation or/and lattice constant, where their direct coupling generates moiré potentials. Moiré materials have emerged as a platform for the discovery of new physics and device concepts, but while moiré materials are highly tunable, once formed, moiré lattices cannot be easily altered. Here we demonstrate the electrostatic imprinting of moiré lattices onto a target monolayer semiconductor.

Journal
Nature Materials
Date Published
Funding Source
DMR-2114535
NNCI-2025233
FA9550-18-1-0480
JPMJCR15F3
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Resonant Ultrasound Spectroscopy for Irregularly Shaped Samples and Its Application to Uranium Ditelluride

Author
Gregorio Simarro
Avi Shragai
Gael Grissonnanche
Ian Hayes
Shanta Saha
Tatsuya Shishidou
Taishi Chen
Satoru Nakatsuji
Sheng Ran
Michael Weinert
Nicholas Butch
Johnpierre Paglione
B. Ramshaw
Abstract

Resonant ultrasound spectroscopy (RUS) is a powerful technique for measuring the full elastic tensor of a given material in a single experiment. Previously, this technique was practically limited to regularly shaped samples such as rectangular parallelepipeds, spheres, and cylinders [W. M. Visscher et al. J. Acoust. Soc. Am. 90, 2154 (1991)].

Journal
PHYSICAL REVIEW LETTERS
Date Published
Funding Source
DE-SC0020143
S10OD012287
DMR-1719875
DE-SC-0019154
GBMF9071
Group (Lab)
Brad Ramshaw Group