Quantum interference in a Josephson junction with magnetic topological insulator barrier*

Transport properties of a Josephson junction consisting of two s-wave superconductors separated by an even-layer MnBi₂Te₄ (MBT) are studied. We calculate the supercurrent in the presence of a perpendicular magnetic field and find that its quantum interference can be used to distinguish different electronic (and magnetic) states of the MBT. In the antiferromagnetic state, the MBT is an axion insulator supporting an extended “hinge” supercurrent, which leads to a sinusoidal interference pattern decaying with an increasing field. In the ferromagnetic state, the MBT is a Chern insulator where the unbalanced chiral supercurrents on opposite edges give rise to a highly asymmetric interference. If the MBT turns into a metal as the Fermi level is tuned into the conduction band, the interference exhibits a Fraunhofer pattern due to the uniformly distributed bulk supercurrent. Our findings reveal a strong indicator to experimentally identify different phases in a magnetic topological insulator.