Observation of a Reconstructed Chern Insulator in Twisted Bilayer MoTe2

TL;DR

This study explores twisted bilayer MoTe2 at a larger twist angle of 4.54°, revealing multiple topological Chern-insulating states and a fractional Chern insulator, thus expanding the understanding of topological phases in moire materials.

Contribution

It demonstrates the existence of various Chern-insulating states at larger twist angles, broadening the topological phase diagram of twisted bilayer MoTe2 and showing its potential for topological state engineering.

Findings

Multiple Chern-insulating states with C=1 at specific moire fillings

Observation of a fractional Chern insulator at v=-2/3 under magnetic field

Large-angle moire superlattices can host robust topological states

Abstract

Twisted bilayer MoTe2 is a prototypical moire material in which long-wavelength superlattices amplify electron correlations, enabling a wealth of emergent quantum phases. To date, experimental efforts have focused primarily on small twist angles (typically smaller than 4deg ), whereas the larger-angle regime-where moire bands become more dispersive and correlations are reduced-has remained largely unexplored. Here we chart the topological phase space of tMoTe2 at a relatively large twist angle of approximately 4.54deg, accessing a moderately correlated regime with enhanced bandwidth. In contrast to small-angle devices that predominantly host fractional quantum anomalous Hall or spin Hall responses, we uncover multiple Chern-insulating states with C = 1 at moire fillings v = -1, -0.53 and -1/2. Strikingly, at v = -2/3 a magnetic field induces a fractional Chern insulator accompanied by an insulator-metal transition. Our results broaden the topological phase diagram of tMoTe2 and establish large-angle moire superlattices as a versatile platform for engineering robust topological states beyond the strong-correlation limit.