Spin fluctuations in quantized transport of magnetic topological insulators

TL;DR

This paper investigates how thermal spin fluctuations, acting as frozen disorders, influence quantized transport in magnetic topological insulators, revealing effects overlooked by mean-field theories and explaining recent experimental observations.

Contribution

It demonstrates that thermal spin fluctuations significantly affect quantized transport, challenging mean-field predictions and offering new insights into phase transitions in magnetic topological insulators.

Findings

Thermal spin fluctuations reduce the temperature for quantized transport onset.

Spin fluctuations act as frozen disorders, scattering electrons.

Mean-field exchange gap considerations are insufficient for phase transition predictions.

Abstract

In magnetic topological insulators, quantized electronic transport is interwined with spontaneous magnetic ordering, as magnetization controls band gaps, hence band topology, through the exchange interaction. We show that considering the exchange gaps at the mean-field level is inadequate to predict phase transitions between electronic states of distinct topology. Thermal spin fluctuations disturbing the magnetization can act as frozen disorders that strongly scatter electrons, reducing the onset temperature of quantized transport appreciably even in the absence of structural impurities. This effect, which has hitherto been overlooked, provides an alternative explanation of recent experiments on intrinsic magnetic topological insulators.