# Flat Chern Band From Twisted Bilayer MnBi$_2$Te$_4$

## TL;DR

This paper models twisted bilayer MnBi₂Te₄, revealing highly tunable Chern bands and flat bands at specific twist angles, offering a platform for topological phases and quantum anomalous Hall effects.

## Contribution

It introduces a continuum model for twisted bilayer MnBi₂Te₄, demonstrating the emergence of flat Chern bands and topological phases at certain twist angles.

## Key findings

- Chern number up to 3 in the band structure
- Flat bands with Chern number ±1 at 1° twist angle
- Potential realization of topological phases like fractional Chern insulators

## Abstract

We construct a continuum model for the Moir\'e superlattice of twisted bilayer MnBi$_2$Te$_4$, and study the band structure of the bilayer in both ferromagnetic (FM) and antiferromagnetic (AFM) phases. We find the system exhibits highly tunable Chern bands with Chern number up to $3$. We show that a twist angle of $1^\circ$ turns the highest valence band into a flat band with Chern number $\pm1$ that is isolated from all other bands in both FM and AFM phases. This result provides a promising platform for realizing time-reversal breaking correlated topological phases, such as fractional Chern insulator and $p+ip$ topological superconductor. In addition, our calculation indicates that the twisted stacking facilitates the emergence of quantum anomalous Hall effect in MnBi$_2$Te$_4$.