Gate-electric-field and magnetic-field control of versatile topological phases in a semi-magnetic topological insulator

TL;DR

This study demonstrates how dual-gate electric and magnetic fields can precisely control topological phases in a semi-magnetic topological insulator heterostructure, enabling transitions among QAH, axion insulator, and parity anomaly states.

Contribution

It introduces a method for independently tuning the top and bottom surface states to induce various topological phase transitions in magnetic topological insulators.

Findings

Hall conductivity approaches half-integer quantization at specific Fermi energies

Dual-gate control aligns band structures with quantum Hall states

Multiple topological phase transitions observed among QAH, axion insulator, and parity anomaly states

Abstract

Surface states of a topological insulator demonstrate interesting quantum phenomena, such as the quantum anomalous Hall (QAH) effect and the quantum magnetoelectric effect. Fermi energy tuning plays a role in inducing phase transitions and developing future device functions. Here, we report on controlling the topological phases in a dual-gate field-effect transistor of a semi-magnetic topological insulator heterostructure. The heterostructure consists of magnetized one-surface and non-magnetic other-surface. By tuning the Fermi energy to the energy gap of the magnetized surface, the Hall conductivity $\sigma_{xy}$ becomes close to the half-integer quantized Hall conductivity $e^2/2h$, exemplifying parity anomaly. The dual-gate control enables the band structure alignment to the two quantum Hall states with $\sigma_{xy} = e^2/h$ and 0 under a strong magnetic field. These states are topologically equivalent to the QAH and axion insulator states, respectively. Precise and independent control of the band alignment of the top and bottom surfaces successively induces various topological phase transitions among the QAH, axion insulator, and parity anomaly states in magnetic topological insulators.