Current scaling of the topological quantum phase transition between a quantum anomalous Hall insulator and a trivial insulator

TL;DR

This study investigates the current-driven quantum phase transition between a quantum anomalous Hall insulator and a trivial insulator, revealing critical behavior and scaling laws through experimental measurements.

Contribution

It provides the first detailed current scaling analysis of the quantum phase transition in magnetic topological insulators, including critical exponents.

Findings

Transition curves cross at a single point indicating quantum criticality

Scaling exponent for excitation current determined from power law dependence

Critical exponents for localization and coherence lengths evaluated

Abstract

We report a current scaling study of a quantum phase transition between a quantum anomalous Hall insulator and a trivial insulator on the surface of a heterostructure film of magnetic topological insulators. The transition was observed by tilting the magnetization while measuring the Hall conductivity $\sigma_{xy}$. The transition curves of $\sigma_{xy}$ taken under various excitation currents cross each other at a single point, exemplifying a quantum critical behavior of the transition. The slopes of the transition curves follow a power law dependence of the excitation current, giving a scaling exponent. Combining with the result of the previous temperature scaling study, critical exponents $\nu$ for the localization length and $p$ for the coherence length are separately evaluated as $\nu$ = 2.8 $\pm$ 0.3 and $p$ = 3.3 $\pm$ 0.3.