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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

Valley-Coherent Quantum Anomalous Hall State in AB-Stacked MoTe2/ W S e2 Bilayers

Cornell Affiliated Author(s)
Author
Z. Tao
B. Shen
S. Jiang
T. Li
L. Li
L. Ma
W. Zhao
J. Hu
K. Pistunova
K. Watanabe
T. Taniguchi
T.F. Heinz
K.F. Mak
J. Shan
Abstract

Moiré materials provide fertile ground for the correlated and topological quantum phenomena. Among them, the quantum anomalous Hall (QAH) effect, in which the Hall resistance is quantized even under zero magnetic field, is a direct manifestation of the intrinsic topological properties of a material and an appealing attribute for low-power electronics applications. The QAH effect has been observed in both graphene and transition metal dichalcogenide (TMD) moiré materials. It is thought to arise from the interaction-driven valley polarization of the narrow moiré bands.

Journal
Physical Review X
Date Published
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Realization of the Haldane Chern insulator in a moiré lattice

Author
W. Zhao
K. Kang
Y. Zhang
P. Knuppel
Z. Tao
L. Li
C.L. Tschirhart
E. Redekop
K. Watanabe
T. Taniguchi
A.F. Young
J. Shan
K.F. Mak
Abstract

The Chern insulator displays a quantized Hall effect without Landau levels. Theoretically, this state can be realized by engineering complex next-nearest-neighbour hopping in a honeycomb lattice—the so-called Haldane model. Despite its profound effect on the field of topological physics and recent implementation in cold-atom experiments, the Haldane model has not yet been realized in solid-state materials.

Journal
Nature Physics
Date Published
Funding Source
DMR-1807810
FA9550-19-1-0390
FA9550-20-1-0219
GBMF9471
W911NF-20-2-0166
DE-SC0019481
NNCI-2025233
JPMJCR15F3
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Switchable moiré potentials in ferroelectric WTe2/WSe2 superlattices

Cornell Affiliated Author(s)
Author
K. Kang
W. Zhao
Y. Zeng
K. Watanabe
T. Taniguchi
J. Shan
K.F. Mak
Abstract

Moiré materials with superlattice periodicity many times the atomic length scale have shown strong electronic correlations and band topology with unprecedented tunability. Non-volatile control of the moiré potentials could allow on-demand switching of superlattice effects but has remained challenging to achieve. Here we demonstrate the switching of the correlated and moiré band insulating states, and the associated nonlinear anomalous Hall effect, by the ferroelectric effect.

Journal
Nature Nanotechnology
Date Published
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Gate-tunable heavy fermions in a moiré Kondo lattice

Cornell Affiliated Author(s)
Author
W. Zhao
B. Shen
Z. Tao
Z. Han
K. Kang
K. Watanabe
T. Taniguchi
K.F. Mak
J. Shan
Abstract

The Kondo lattice—a matrix of local magnetic moments coupled through spin-exchange interactions to itinerant conduction electrons—is a prototype of strongly correlated quantum matter1–4. Usually, Kondo lattices are realized in intermetallic compounds containing lanthanide or actinide1,2. The complex electronic structure and limited tunability of both the electron density and exchange interactions in these bulk materials pose considerable challenges to studying Kondo lattice physics.

Journal
Nature
Date Published
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Intrinsic spin Hall torque in a moiré Chern magnet

Cornell Affiliated Author(s)
Author
C.L. Tschirhart
E. Redekop
L. Li
T. Li
S. Jiang
T. Arp
O. Sheekey
T. Taniguchi
K. Watanabe
M.E. Huber
K.F. Mak
J. Shan
A.F. Young
Abstract

In spin torque magnetic memories, electrically actuated spin currents are used to switch a magnetic bit. Typically, these require a multilayer geometry including both a free ferromagnetic layer and a second layer providing spin injection. For example, spin may be injected by a non-magnetic layer exhibiting a large spin Hall effect, a phenomenon known as spin–orbit torque. Here we demonstrate a spin–orbit torque magnetic bit in a single two-dimensional system with intrinsic magnetism and strong Berry curvature.

Journal
Nature Physics
Date Published
Group (Lab)
Jie Shan Group
Kin Fai Mak Group

Evidence of frustrated magnetic interactions in a Wigner-Mott insulator

Cornell Affiliated Author(s)
Author
Yanhao Tang
Kaixiang Su
Lizhong Li
Yang Xu
Song Liu
Kenji Watanabe
Takashi Taniguchi
James Hone
Chao-Ming Jian
Cenke Xu
Kin Mak
Jie Shan
Abstract

Electrons in two-dimensional semiconductor moiré materials are more delocalized around the lattice sites than those in conventional solids1,2. The non-local contributions to the magnetic interactions can therefore be as important as the Anderson superexchange3, which makes the materials a unique platform to study the effects of competing magnetic interactions3,4. Here we report evidence of strongly frustrated magnetic interactions in a Wigner–Mott insulator at a two-thirds (2/3) filling of the moiré lattice in angle-aligned WSe2/WS2 bilayers.

Journal
Nature Nanotechnology
Date Published
Group (Lab)
Chao-Ming Jian Group
Jie Shan Group
Kin Fai Mak Group

Exciton density waves in Coulomb-coupled dual moiré lattices

Cornell Affiliated Author(s)
Author
Y. Zeng
Z. Xia
R. Dery
K. Watanabe
T. Taniguchi
J. Shan
K.F. Mak
Abstract

Strongly correlated bosons in a lattice are a platform that can realize rich bosonic states of matter and quantum phase transitions1. While strongly correlated bosons in a lattice have been studied in cold-atom experiments2–4, their realization in a solid-state system has remained challenging5. Here we trap interlayer excitons–bosons composed of bound electron–hole pairs, in a lattice provided by an angle-aligned WS2/bilayer WSe2/WS2 multilayer. The heterostructure supports Coulomb-coupled triangular moiré lattices of nearly identical period at the top and bottom interfaces.

Journal
Nature Materials
Date Published
Funding Source
DMR-2114535
N00014-21-1-2471
NNCI-2025233
DE-SC0019481
JPMJCR15F3
Group (Lab)
Jie Shan Group
Kin Fai Mak Group