Abstract:

Research on axion insulators in condensed matter physics has generated widespread attention in recent years. Axion insulators exhibit an electromagnetic response similar to that of the hypothetical elementary particle-axion-proposed in high-energy physics, leading to phenomena such as half-quantized surface Hall conductivity or topological magnetoelectric effects in the system. Recently, transport experiments on three-dimensional magnetic topological insulator heterojunctions and intrinsic magnetic topological insulators like MnBi2Te4 have revealed signatures of the existence of axion insulators. However, precise measurement of the half-quantized electromagnetic response of axion insulators remains challenging. In this review, we summarize the theoretical and experimental progress in axion insulator research within magnetic topological insulating materials. We discuss the excitation of halfquantized edge currents in axion insulators due to the bulk-boundary correspondence, as well as a transport theory based on half-magnetic topological insulators for half-quantized Hall conductivity. Finally, we explore disorder-induced phase transitions in axion insulators, including the universality classes of two-dimensional quantum Hall-like conductivity transitions on the surface, and propose methods to detect axion insulators using the universal characteristics of these phase transitions.

Key words: axion insulator, disorder, Half-quantized, Goos-Hanchen shift, topological magnetoelectric effect, quantum transpor