Relaxation-driven flat bands and topology in moiré transition metal dichalcogenide heterobilayers
Abstract
Moiré transition metal dichalcogenide (TMD) heterobilayers are commonly modeled by a continuum theory that yields topologically trivial bands, in contrast to their homobilayer counterparts which host topological bands and fractional Chern insulators (FCI). We show this conclusion is an artifact of neglecting the pseudomagnetic field generated by lattice relaxation, an effect intrinsic to every moiré material. We develop a continuum model that resolves relaxation into three channels: a modified moiré potential with higher Fourier harmonics, a pseudoelectric (scalar deformation) potential, and a pseudomagnetic (vector) potential. Using WSe2/WS2 as a prototype, we find that the pseudomagnetic field alone gaps the third and fourth valence bands with Chern numbers ± 1 over a broad range of twist angle and lattice mismatch, while the moiré potential correction and pseudoelectric potential narrow the bandwidth and enhance the bandgaps, which survive many-body interactions using neural-network variational Monte Carlo calculations. Relaxation also smoothens the Berry curvature and quantum metric relative to the rigid model, moving the band closer to the ideal Chern limit, beneficial for the quantum anomalous Hall effect, FCI states, and flat-band superconductivity when filled to higher bands. Our work establishes a new framework that connects first-principles calculations, through the continuum model, to many-body observables. Using this framework, we show moiré heterobilayers as a new class of topological materials whose topology is driven entirely by intrinsic lattice relaxation.
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BibTeX
@misc{luskin2026relaxationdriven,
title = {{Relaxation-driven flat bands and topology in moiré transition metal dichalcogenide heterobilayers}},
author = {Mitchell Luskin and Max Geier and Liang Fu and Ziyan Zhu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.08917},
eprint = {2608.08917},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.08917},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Relaxation-driven flat bands and topology in moiré transition metal dichalcogenide heterobilayers
AU - Mitchell Luskin
AU - Max Geier
AU - Liang Fu
AU - Ziyan Zhu
PY - 2026
DA - 2026/10/03
PB - arXiv
DO - 10.48550/arxiv.2608.08917
UR - https://arxiv.org/abs/2608.08917
AB - Moiré transition metal dichalcogenide (TMD) heterobilayers are commonly modeled by a continuum theory that yields topologically trivial bands, in contrast to their homobilayer counterparts which host topological bands and fractional Chern insulators (FCI). We show this conclusion is an artifact of neglecting the pseudomagnetic field generated by lattice relaxation, an effect intrinsic to every moiré material. We develop a continuum model that resolves relaxation into three channels: a modified moiré potential with higher Fourier harmonics, a pseudoelectric (scalar deformation) potential, and a pseudomagnetic (vector) potential. Using WSe_2/WS_2 as a prototype, we find that the pseudomagnetic field alone gaps the third and fourth valence bands with Chern numbers ± 1 over a broad range of twist angle and lattice mismatch, while the moiré potential correction and pseudoelectric potential narrow the bandwidth and enhance the bandgaps, which survive many-body interactions using neural-network variational Monte Carlo calculations. Relaxation also smoothens the Berry curvature and quantum metric relative to the rigid model, moving the band closer to the ideal Chern limit, beneficial for the quantum anomalous Hall effect, FCI states, and flat-band superconductivity when filled to higher bands. Our work establishes a new framework that connects first-principles calculations, through the continuum model, to many-body observables. Using this framework, we show moiré heterobilayers as a new class of topological materials whose topology is driven entirely by intrinsic lattice relaxation.
ER -