Magic in twisted transition metal dichalcogenide bilayers

Trithep Devakul; Valentin Crépel; Yang Zhang; Liang Fu

doi:10.1038/s41467-021-27042-9

Magic in twisted transition metal dichalcogenide bilayers

Nat Commun. 2021 Nov 18;12(1):6730. doi: 10.1038/s41467-021-27042-9.

Authors

Trithep Devakul^#¹, Valentin Crépel², Yang Zhang^#², Liang Fu³

Affiliations

¹ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA. tdevakul@mit.edu.
² Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
³ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA. liangfu@mit.edu.

^# Contributed equally.

Abstract

The long-wavelength moiré superlattices in twisted 2D structures have emerged as a highly tunable platform for strongly correlated electron physics. We study the moiré bands in twisted transition metal dichalcogenide homobilayers, focusing on WSe₂, at small twist angles using a combination of first principles density functional theory, continuum modeling, and Hartree-Fock approximation. We reveal the rich physics at small twist angles θ < 4^∘, and identify a particular magic angle at which the top valence moiré band achieves almost perfect flatness. In the vicinity of this magic angle, we predict the realization of a generalized Kane-Mele model with a topological flat band, interaction-driven Haldane insulator, and Mott insulators at the filling of one hole per moiré unit cell. The combination of flat dispersion and uniformity of Berry curvature near the magic angle holds promise for realizing fractional quantum anomalous Hall effect at fractional filling. We also identify twist angles favorable for quantum spin Hall insulators and interaction-induced quantum anomalous Hall insulators at other integer fillings.