Programmable Quantum Anomalous Hall Insulator in Twisted Crystalline Flatbands

TL;DR

This paper reports on twisted double rhombohedral-trilayer-graphene as a new platform for programmable topological phases, revealing tunable Chern insulators with various Chern numbers and exotic symmetry-breaking phenomena in flatband systems.

Contribution

It introduces a novel twisted crystalline flatbands system exhibiting rich moiré-dependent topological phenomena and demonstrates tunable high Chern insulators with potential quantum applications.

Findings

Observation of Chern insulator with C=3 at v=1

Discovery of a hidden order quenching the Chern insulator

Multiple Chern insulators with C=1 at fractional fillings

Abstract

The isospin flavors in condensed matters can be continuously broken, forming various symmetry-broken quantum states. In moir\'e crystals, the competition between different isospin configurations can be effectively tuned by the twist angles and staciking orders. Here we report twisted double rhombohedral-trilayer-gaphene as a new twisted crystalline flatbands system showing rich moir\'e dependent topological phenomena. In devices with small twist angles, programmable Chern insulators with Chern number C = 3 at integer moir\'e filling v = 1 have been observed. We have further revealed an exotic hidden order which can quench the Chern insulator as well as multiple first-order transitions between different symmetry-broken phases. Interestly, in the device with a slightly larger twist angle, multiple Chern insulators with C = 1 at fractional moir\'e fillings including v = 1/4, 1/3 and 1/2 have been observed, whereas the Chern insulator at v = 1 is abscent. Our study demonstrated the twisted flatbands form rhombohedral-multilayer-graphene as a new platform to study tunable high Chern insulators as well as new devices for quantum storage and computation.