Mapping twist-tuned multiband topology in bilayer WSe$_2$

TL;DR

This study investigates twisted bilayer WSe$_2$ at small angles, revealing multiple topological bands and Chern insulators, and demonstrates electric-field-induced topological phase transitions, establishing a tunable platform for correlated topological phases.

Contribution

It provides the first local electronic compressibility measurements of twisted bilayer WSe$_2$ at small angles, mapping its topological phase diagram and demonstrating tunable topological transitions.

Findings

Multiple topological bands with Chern insulators near 1.23° twist angle

Electric field induces a topological quantum phase transition

Establishment of a tunable platform for correlated topological phases

Abstract

Semiconductor moir\'e superlattices have been shown to host a wide array of interaction-driven ground states. However, twisted homobilayers have been difficult to study in the limit of large moir\'e wavelength, where interactions are most dominant. Here, we conduct local electronic compressibility measurements of twisted bilayer WSe$_2$ (tWSe$_2$) at small twist angles. We demonstrate multiple topological bands which host a series of Chern insulators at zero magnetic field near a 'magic angle' around $1.23^\circ$. Using a locally applied electric field, we induce a topological quantum phase transition at one hole per moir\'e unit cell. Our work establishes the topological phase diagram of a generalized Kane-Mele-Hubbard model in tWSe$_2$, demonstrating a tunable platform for strongly correlated topological phases.