Quantum interference in a superconductor-${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$-superconductor Josephson junction

TL;DR

This study investigates quantum interference patterns in a superconductor-MnBi2Te4-superconductor Josephson junction, revealing distinct behaviors depending on the magnetic state of the MnBi2Te4 layer, which can serve as phase indicators.

Contribution

The paper introduces a detailed analysis of supercurrent interference patterns in a Josephson junction with MnBi2Te4, highlighting how magnetic states influence quantum interference.

Findings

Antiferromagnetic MBT shows sinusoidal interference decaying with magnetic field.

Ferromagnetic MBT exhibits asymmetric interference due to chiral edge supercurrents.

Metallic MBT results in Fraunhofer interference pattern from bulk supercurrent.

Abstract

We study the transport properties of a Josephson junction consisting of two identical $s$-wave superconductors separated by an even-layer ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ (MBT). Using recursive Green's function method, we calculate the supercurrent in the presence of a perpendicular magnetic field and find that its quantum interference exhibits distinct patterns when the MBT is in different magnetic states. In the antiferromagnetic state, the MBT is an axion insulator supporting an extended "hinge" supercurrent, which leads to a sinusoidal interference pattern decaying with the field strength. In the ferromagnetic state, the MBT is a Chern insulator and the unbalanced chiral supercurrents on opposite edges give rise to a highly asymmetric interference pattern. 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 work unravels a strong indicator to identify different phases in the MBT and can be verified directly by experiments.