Speaker: Shuigang Xu, Westlake University

Time: 15:00 p.m., April 30, 2025, GMT+8

Venue: Room w563, Physics building, Peking University

Abstract: 

Topological flat bands with non-trivial topology and flat band structure hold significant research interest in the field of condensed matter physics, serving as a promising platform for exploring novel quantumstates such as unconventional superconductivity and quantum anomalous Hall effect. In rhombohedral multilayer graphene, the low-energy electronic bands exhibit layer-number-dependent exponential dispersion relations, characterized by pronounced flat band features and giant Berry curvature. However, the intrinsic rhombohedral multilayer graphene suffers from band overlap between its low-energy flat bands and high-energy dispersive bands, which constrains the full manifestation of its topological properties.
In this talk, I will introduce the construction of isolated flat Chern bands in rhombohedral multilayer graphene by introducing moiré superlattices. By this way, we observe emergent quantum phenomena including layer-polarized ferromagnetism, chirality-switchable Chern insulators, and high-Chern-number quantum anomalous Hall states. Particularly, in rhombohedral heptalayer graphene, strong electron correlations can spontaneously open topological gaps, leading to the formation of an "anomalous Hall crystal" phase. This discovery not only provides new insights into the coupling mechanisms between electronic correlations and topological order but also opens new avenues for tuning Chern insulators.

Source: School of Physics, PKU