Scaling behavior of the quantum phase transition from a quantum anomalous Hall insulator to an axion insulator.*

We performed the scaling behavior study of quantum phase transition from quantum anomalous Hall state(QAHS) to axion insulator state in magnetic topological insulator sandwich samples. A power-law dependence of the derivative of longitudinal resistance with magnetic field on temperature was observed at the transition point. We extracted the critical exponent κ ~ 0.38±0.02, which agrees well with the recent high precision calculation result of ν ~ 2.6 using the Chalker-Coddington network model in quantum Hall system. We also measured the resistance of the axion insulator state, which is as high as 1.3 GΩ at 50 mK using a quasi-DC measurement method. Our work indicates that the QAHS to axion insulator state transition shares the same universality class with the plateau to plateau transition in quantum Hall system.[1]
[1] Wu, X. et al, Nat. Commun. 11, 4532(2020)