Ting Cao

Switching the bulk Chern number in topological materials is of central importance for the design of topological electronic devices. Motivated by recent observations of integer and fractional quantum anomalous Hall effects in twisted transition metal dichalcogenides, we realize the switching of valley Chern number through sliding and gating in alternately twisted tetralayer (ATT) MoTe2. Using density functional theory (DFT) calculations, we show that the Chern number of the first K-valley moiré band evolves from +1 to −1 under the interlayer sliding. Furthermore, an applied electric field can switch the valley Chern number from −1 to +1. Based on the developed continuum model, we reveal that these switching behaviors are caused by the sliding- and gate-dependent intralayer moiré potential distributions across the layers. Our results establish ATT MoTe2 as a promising platform for engineering moiré band topologies through the design of moiré potentials with sliding in multilayer moiré systems.

Berry curvature in twisted molybdenum ditelluride drives the oppositely charged particles in an exciton in opposite transverse directions, producing a dipole moment of approximately 150 Debye.

Strongly correlated topological phases of matter are central to modern condensed matter physics and quantum information technology but often challenging to probe and control in material systems. The experimental difficulty of accessing these phases has motivated the use of engineered quantum platforms for simulation and manipulation of exotic topological states. Among these, the Laughlin state stands as a cornerstone for topological matter, embodying fractionalization, anyonic excitations, and incompressibility. Although its bosonic analogs have been realized on programmable quantum simulators, a genuine fermionic Laughlin state has yet to be demonstrated on a quantum processor. Here, we realize the ν = 1/3 fermionic Laughlin state on IonQ’s trapped-ion quantum computer using an efficient and scalable Hamiltonian variational ansatz with 369 two-qubit gates on a 16-qubit circuit. Employing symmetry-verification error mitigation, we extract key observables that characterize the Laughlin state, including correlation hole, bulk-edge correspondence, and topological entanglement entropy, with strong agreement to exact diagonalization benchmarks. This work demonstrates an end-to-end workflow to simulate material-intrinsic topological orders and provides a starting point to explore its dynamics and excitations on digital quantum processors.

We introduce a physics-informed training-data generation strategy that efficiently captures the complete interlayer interactions in multilayer moiré systems, enabling a machine-learning force field transferable across layer numbers and stacking configurations, beyond twist angles. Applying this to multilayer twisted MoTe ₂ (tMoTe ₂ ), we identify a structural and electronic stratification: The two moiré interface (MI) layers retain substantial lattice reconstruction even in thick multilayers, while outer bulk-like layers show rapidly attenuated distortions. Surprisingly, this stratification becomes strongest not in the ultrasmall twist angle regime (≲1 ^° ), where in-plane domain formation is well known, but rather at intermediate angles (2 to 5 ^° ). Simultaneously, interlayer hybridization across the MI–bulk boundary is strongly suppressed, leading to electronic isolation. In twisted double bilayer MoTe ₂ , this stratification gives rise to coexisting honeycomb and triangular lattice motifs in the frontier valence bands. We further demonstrate that twist angle and weak gating can create energy shift of bands belonging to the two motifs, producing Chern band reordering and nonlinear electric polarization with modest hole doping. Our approach allows efficient simulation of multilayer moiré systems and reveals structural–electronic separation phenomena absent in bilayer systems.

Recent observations of quantum anomalous Hall effects in moiré systems have revealed the emergence of interaction-driven ferromagnetism with significant orbital contributions. To capture this physics, we extend the modern theory of orbital magnetization to Hartree-Fock states and show that the standard expression remains valid with Hartree-Fock orbitals and Hamiltonians. Then, we benchmark our theory against the extended Kane-Mele-Hubbard model in a weak field, which yields excellent agreement with direct numerical calculations. Applying our theory to twisted MoTe_{2} bilayers, we find orbital magnetization of order one Bohr magneton per moiré cell with a nonmonotonic twist-angle dependence. Our work establishes a general theory of orbital magnetization in interacting moiré systems and provides quantitative guidance for interpreting recent experiments.

Moiré superlattices of transition-metal dichalcogenide bilayers host strong Coulomb interactions residing in narrow electron bands, leading to correlated insulating states at fractional carrier doping densities, known as generalized Wigner crystals. In excited states, the formation of moiré excitons can be fundamentally shaped by the Wigner-crystal ground states, manifesting an intricate interplay between electronic and excitonic correlations. However, the microscopic description of these Wigner crystalline excitons (WCEs) remains elusive, largely subject to speculations, and is further needed for the understanding of exotic excitonic phases (e.g., exciton insulators and exciton density waves) and their unique properties (e.g., anomalous exciton diffusion). Here, using first-principles many-body GW –Bethe–Salpeter equation calculations, we directly reveal the internal structures of WCEs in angle-aligned MoSe ₂ /MoS ₂ moiré heterostructure at hole fillings of 1/3 and 2/3. Our results uncover the propagation of correlation effects from the ground state to excited states, shaping the real-space characteristics of WCEs. The strong two-particle excitonic correlations dominate over the kinetic energy of free electron–hole pairs, in analog to the strong single-particle correlations of flat bands. We propose that such unusual excited-state correlation effects of WCEs can be experimentally probed by photocurrent tunneling microscopy (PTM). Our work provides a microscopic understanding of strongly correlated WCEs, suggesting them as a highly tunable mixed boson-fermion platform to study many-body interactions and phenomena.

Recent research suggests the possibility of the two-dimensional breathing-Kagome magnet Nb ₃ Cl ₈ hosting a quantum spin liquid state, warranting further study into its magnetic properties. Using ab initio calculations, we show that monolayer Nb ₃ Cl ₈ has short-range antiferromagnetic (AFM) correlations among Nb ₃ trimers with S = 1 / 2 , and becomes magnetically frustrated due to the underlying effective triangular lattice geometry, and is evidenced by a frustration index of f > 1. The high-temperature susceptibility shows a negative Weiss temperature from Monte Carlo calculations. Considering spin–orbit coupling, we investigate the magnetic anisotropy, including anisotropic exchange, single-ion anisotropy and the Dzyaloshinskii–Moriya interaction (DMI) using the four-state energy mapping formalism. Although the elements have relatively small atomic numbers, the DMI is comparable in magnitude to the anisotropic exchange. Additionally, we show that biaxial strain tunes the short-range correlations between AFM, paramagnetic and ferromagnetic. These findings strengthen our understanding of Nb ₃ Cl ₈ and advance its applications in current condensed matter physics and materials science research, including nanoscale mechanical and spintronics applications.

Fractionalization of the electron charge e is one of the most striking phenomena arising from strong electron–electron interactions. A celebrated example is the emergence of anyons with fractional charges in fractional quantum Hall effect (FQHE) states^{1,2,3,4,5,6,7,8,9,10,11,12,13}. Recently, zero-field fractional Chern insulators (FCIs)^{14,15,16,17,18,19}, lattice analogues of the FQHE states that form without Landau levels, have been realized^20,21. FCIs provide a unique platform to investigate anyons, yet their detection remains a challenge. Here we report the observation of anyon–trions, a new type of excitonic complex formed by binding a trion with a fractional charge in twisted MoTe₂ bilayers. Photoluminescence spectroscopy of quantum-confined excitons reveals emergent peaks that appear only within slightly doped FCI states. The new spectral features are red-shifted relative to the trions in undoped FCIs, but share the same electric field, temperature and magnetic field dependence. These observations suggest their origin as trions binding with elementary quasi-particles, that is, anyon–trions. Crucially, the ratio of binding energies between the anyon–trions in the −2/3 and −3/5 FCI states matches the expected fractional charge ratio of e/3 to e/5. This provides strong evidence for fractional charges in FCI—an essential property of anyons. Our results address a fundamental question in FCI physics and establish trion spectroscopy as a powerful probe of fractionally charged excitations, complementary to transport- and tunnelling-based approaches.