Geometric Effect on Quantum Anomalous Hall States in Magnetic Topological Insulators

TL;DR

This paper investigates how geometric mismatches and external factors influence the dissipative edge states in quantum anomalous Hall effect within magnetic topological insulators, combining numerical modeling with experimental insights.

Contribution

It reveals that geometric mismatch causes additional scattering leading to dissipation in QAHE, and shows how magnetic fields and disorder can suppress this effect.

Findings

Geometric mismatch causes additional scattering and dissipation.

Magnetic fields and disorder suppress longitudinal resistance.

Results align with experimental observations.

Abstract

An intriguing observation on the quantum anomalous Hall effect (QAHE) in magnetic topological insulators (MTIs) is the dissipative edge states, where quantized Hall resistance is accompanied by nonzero longitudinal resistance. We numerically investigate this dissipative behavior of QAHE in MTIs with a three-dimensional tight-binding model and non-equilibrium Greens function formalism. It is found that, in clean samples, the geometric mismatch between the detecting electrodes and the MTI sample leads to additional scattering in the central Hall bar, which is similar to the effect of splitting gates in the traditional Hall effect. As a result, while the Hall resistance remains quantized, the longitudinal resistance deviates from zero due to such additional scattering. It is also shown that external magnetic fields as well as disorder scattering can suppress the dissipation of the longitudinal resistance. These results are in good agreement with previous experimental observations and provide insight on the fabrication of QAHE devices.