Asymmetric Josephson Effect in Inversion Symmetry Breaking Topological Materials

TL;DR

This paper investigates the asymmetric Josephson effect in inversion symmetry breaking topological materials, revealing that critical currents differ based on direction and magnetic field, leading to potential detection methods for symmetry breaking.

Contribution

It introduces the asymmetric Josephson effect (AJE) in topological materials with broken inversion symmetry, highlighting a novel phenomenon not previously characterized.

Findings

Critical currents differ for opposite directions in symmetry-broken topological materials.

Critical currents violate the magnetic field symmetry relation |I_c(B)| ≠ |I_c(-B)|.

Asymmetric Fraunhofer patterns emerge due to AJE.

Abstract

Topological materials which possess topologically protected surface states have attracted much attention in recent years. In this work, we study the critical current of superconductor/inversion symmetry breaking topological material/superconductor junctions. We found surprisingly that, in topological materials with broken inversion symmetry, the magnitude of the critical Josephson currents $|I^{+}_c(B)|$ at fixed magnetic field $B$ is not the same for critical currents $|I^{-}_c(B)|$ flowing in the opposite direction. Moreover, the critical currents violate the $| I_{c}^{\pm}(B)| = |I_{c}^{\pm}(-B)|$ relation and give rise to asymmetric Fraunhofer patterns. We call this phenomenon asymmetric Josephson effect (AJE). AJE can be use to detect inversion symmetry breaking in topological materials such as in quantum spin Hall systems and Weyl semimetals.