Visualizing and manipulating chiral interface states in a moir\'e quantum anomalous Hall insulator

TL;DR

This paper demonstrates the direct imaging and manipulation of chiral interface states in a moiré quantum anomalous Hall insulator made from twisted monolayer-bilayer graphene, revealing topological properties through STM techniques.

Contribution

It introduces a method to control and visualize chiral interface states in a moiré system, advancing understanding of topological states in correlated materials.

Findings

Chiral interface states can be directly imaged using STM.

Chern domains can be manipulated with STM tip pulses.

The length scale of valley polarization reversal is characterized.

Abstract

Moir\'e systems made from stacked two-dimensional materials host novel correlated and topological states that can be electrically controlled via applied gate voltages. We have used this technique to manipulate Chern domains in an interaction-driven quantum anomalous Hall insulator made from twisted monolayer-bilayer graphene (tMBLG). This has allowed the wavefunction of chiral interface states to be directly imaged using a scanning tunneling microscope (STM). To accomplish this tMBLG carrier concentration was tuned to stabilize neighboring domains of opposite Chern number, thus providing topological interfaces completely devoid of any structural boundaries. STM tip pulse-induced quantum dots were utilized to induce new Chern domains and thereby create new chiral interface states with tunable chirality at predetermined locations. Theoretical analysis confirms the chiral nature of observed interface states and enables the determination of the characteristic length scale of valley polarization reversal across neighboring tMBLG Chern domains. tMBLG is shown to be a useful platform for imaging the exotic topological properties of correlated moir\'e systems.