Equilibrium current in a Weyl-semimetal - superconductor heterostructure

TL;DR

This paper investigates the equilibrium current in a heterostructure of magnetic Weyl semimetals and superconductors, revealing how surface states influence current direction and connecting it to the chiral magnetic effect in Weyl superconductors.

Contribution

It demonstrates the sensitivity of equilibrium current to surface states and phases in Weyl-semimetal-superconductor heterostructures, highlighting a real-space realization of the chiral magnetic effect.

Findings

Surface states cause current reversal in topological phases.

Equilibrium current exists across different phases, influenced by surface states.

Connection established between surface states and the chiral magnetic effect.

Abstract

A heterostructure consisting of a magnetic Weyl semimetal and a conventional superconductor exhibits an equilibrium current parallel to the superconductor interface and perpendicular to the magnetization. Analyzing a minimal model, which as a function of parameters may be in a trivial magnetic insulator phase, a Weyl semimetal phase, or a three-dimensional weak Chern insulator phase, we find that the equilibrium current is sensitive to the presence of surface states, such as the topological Fermi-arc states of the Weyl semimetal or the chiral surface states of the weak Chern insulator. While there is a nonzero equilibrium current in all three phases, the appearance of the surface states in the topological regime leads to a reversal of the direction of the current, compared to the current direction for the trivial magnetic insulator phase. We discuss the interpretation of the surface-state contribution to the equilibrium current as a real-space realization of the superconductivity-enabled equilibrium chiral magnetic effect of a single chirality, predicted to occur in bulk Weyl superconductors.