In-Plane Magnetic-Field-Induced Quantum Anomalous Hall Plateau Transition

We study the critical properties of the in-plane magnetic field-induced quantum anomalous Hall (QAH) plateau transition in axion insulators. Take even septuple layer film MnBi${}_2$Te${}_4$ as a concrete example, we find the mirror symmetry breaking from in-plane field could induce axion insulator to QAH insulator transition, which belongs to generic integer quantum Hall plateau transition. The chiral Majorana fermion does not necessarily emerge at the QAH plateau transition in MnBi${}_2$Te${}_4$ due to strong exchange field, but may be quite feasible in its descendent materials MnBi${}_4$Te${}_7$ and MnBi${}_6$Te${}_{10}$.