In-plane magnetic-field-induced quantum anomalous Hall plateau transition

Axion insulator is a new state of quantum matter with a vanishing Chern number but a quantized topological axion response. We study the critical properties of the magnetic-field-induced quantum phase transition in axion insulators. Take the even septuple layer film MnBi2Te4 as a concrete example, We find the mirror symmetry breaking from in-plane magnetic field could induce an axion insulator to quantum anomalous Hall (QAH) insulator transition, which belongs to the generic integer quantum Hall plateau transition. The microscopic model proposed here explains the out-of-plane magnetic-field-induced QAH plateau transition observed in this system experimentally. The chiral Majorana fermion does not necessarily emerge at the QAH plateau transition in MnBi2Te4 due to strong exchange field, but may be quite feasible in its descendent materials MnBi4Te7 and MnBi6Te10.