Asynchronous mass inversion enriched quantum anomalous Hall states in multilayer graphene

TL;DR

This paper proposes an asynchronous mass inversion mechanism driven by interplay of trigonal warping, layer order, and displacement field in multilayer graphene, explaining the origin of various quantum anomalous Hall states and predicting new ones.

Contribution

It introduces a novel asynchronous mass inversion mechanism to explain QAH states in multilayer graphene and predicts new QAH states in related systems.

Findings

The $C=-3$ QAH state arises from asynchronous mass inversion at Dirac cones.

Topological phase transition from $C=-3$ to $C=-5$ is explained by this mechanism.

Prediction of a $C=3$ QAH state in rhombohedral tetralayer graphene.

Abstract

Recently, multilayer graphene systems have attracted significant attention due to the discovery of a variety of intriguing phases, particularly quantum anomalous Hall (QAH) states. In rhombohedral pentalayer graphene (RPG), both QAH states with Chern number $C = -5$ and $C = -3$ have been observed. While the $C = -5$ QAH state is well understood, the origin of the $C = -3$ QAH state remains unclear. In this letter, we propose that the $C = -3$ QAH state, as well as the topological phase transition from $C = -3$ to $C = -5$ state in RPG, arises from an asynchronous mass inversion mechanism driven by the interplay between trigonal warping, staggered layer order, and the displacement field: Trigonal warping splits the low-energy bands of RPG into a central touching point and three satellite Dirac cones. Meanwhile, the coexistence of the staggered layer order and displacement field induces a momentum-dependent effective mass in the low-energy bands. Consequently, mass inversions at the central touching point and the satellite Dirac cones, induced by an increasing displacement field, can occur asynchronously, leading to the formation of the $C = -3$ QAH state and the topological phase transition from QAH state with $C=-3$ to $C=-5$. Additionally, based on this mechanism, we predict the presence of a $C=3$ QAH state in rhombohedral tetralayer graphene (RTG), which can be detected experimentally. Furthermore, this mechanism can also be applied to Bernal tetralayer graphene (BTG), explaining the origin of the observed $C=6$ QAH state.