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

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 $σ_{xy}$. The transition curves of $σ_{xy}$ 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 $ν$ for the localization length and $p$ for the coherence length are separately evaluated as $ν$ = 2.8 $\pm$ 0.3 and $p$ = 3.3 $\pm$ 0.3.

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