Observation of integer and fractional quantum anomalous Hall effects in twisted bilayer MoTe2

TL;DR

This study provides transport evidence for both integer and fractional quantum anomalous Hall effects in twisted bilayer MoTe2, revealing topological states and phase transitions at zero magnetic field in a moiré material.

Contribution

It demonstrates the realization of IQAH and FQAH states in twisted bilayer MoTe2 and explores their electric field-induced phase transitions without external magnetic fields.

Findings

Quantized Hall resistance at moiré filling factors -1 and -2/3.

Electric field induces topological phase transitions.

Observation of distinct minima in longitudinal resistance.

Abstract

The interplay between strong correlations and topology can lead to the emergence of intriguing quantum states of matter. One well-known example is the fractional quantum Hall effect, where exotic electron fluids with fractionally charged excitations form in partially filled Landau levels. The emergence of topological moir\'e flat bands provides exciting opportunities to realize the lattice analogs of both the integer and fractional quantum Hall states without the need for an external magnetic field. These states are known as the integer and fractional quantum anomalous Hall (IQAH and FQAH) states. Here, we present direct transport evidence of the existence of both IQAH and FQAH states in twisted bilayer MoTe2 (AA stacked). At zero magnetic field, we observe well-quantized Hall resistance of h/e2 around moir\'e filling factor {\nu} = -1 (corresponding to one hole per moir\'e unit cell), and nearly-quantized Hall resistance of 3h/2e2 around {\nu} = -2/3, respectively. Concomitantly, the longitudinal resistance exhibits distinct minima around {\nu} = -1 and -2/3. The application of an electric field induces topological quantum phase transition from the IQAH state to a charge transfer insulator at {\nu} = -1, and from the FQAH state to a generalized Wigner crystal state, further transitioning to a metallic state at {\nu} = -2/3. Our study paves the way for the investigation of fractionally charged excitations and anyonic statistics at zero magnetic field based on semiconductor moir\'e materials.