Light-induced half-quantized Hall effect and axion insulator

TL;DR

This paper proposes a method to realize half-quantized Hall effect and axion insulator phases in 3D topological insulators using optical pumping and magnetic doping, supported by numerical band structure analysis.

Contribution

It introduces a practical scheme combining optical and magnetic techniques to control topological phases in 3D topological insulators, enabling new device functionalities.

Findings

Controlled switching between topological phases using circularly polarized light.

Numerical validation of topological phase transitions via band structure and Berry curvature.

Potential for topological transistors with polarization-controlled properties.

Abstract

Motivated by the recent experimental realization of the half-quantized Hall effect phase in a three-dimensional (3D) semi-magnetic topological insulator [M. Mogi et al., Nature Physics 18, 390 (2022)], we propose a scheme for realizing the half-quantized Hall effect and axion insulator in experimentally mature 3D topological insulator heterostructures. Our approach involves optically pumping and/or magnetically doping the topological insulator surface, such as to break time reversal and gap out the Dirac cones. By toggling between left and right circularly polarized optical pumping, the sign of the half-integer Hall conductance from each of the surface Dirac cones can be controlled, such as to yield half-quantized ($0+1/2$), axion ($-1/2+1/2=0$), and Chern ($1/2+1/2=1$) insulator phases. We substantiate our results based on detailed band structure and Berry curvature numerics on the Floquet Hamiltonian in the high-frequency limit. Our paper showcases how topological phases can be obtained through mature experimental approaches such as magnetic layer doping and circularly polarized laser pumping and opens up potential device applications such as a polarization chirality-controlled topological transistor.