Chirality Josephson current due to a novel quantum anomaly in inversion-asymmetric Weyl semimetals

TL;DR

This paper investigates a novel quantum anomaly in inversion-asymmetric Weyl semimetals, revealing a chirality-dependent Josephson current induced by Zeeman fields, with potential applications in chiralitytronics and experimental detection via Fraunhofer patterns.

Contribution

It uncovers a new quantum anomaly leading to a finite chirality Josephson current in Weyl semimetals, driven by Zeeman fields and linked to a $ ext{Z}_2$ symmetry.

Findings

Zeeman fields cause opposite phase shifts for opposite chirality Weyl nodes.

A finite chirality Josephson current exists without phase difference.

The phenomenon can be observed through anomalous Fraunhofer patterns.

Abstract

We study Josephson junctions based on inversion-asymmetric but time-reversal symmetric Weyl semimetals under the influence of Zeeman fields. We find that, due to distinct spin textures, the Weyl nodes of opposite chirality respond differently to an external magnetic field. Remarkably, a Zeeman field perpendicular to the junction direction results in a phase shift of opposite sign in the current-phase relations of opposite chirality. This leads to a finite chirality Josephson current (CJC) even in the absence of a phase difference across the junction. This feature could allow for applications in chiralitytronics. In the long junction and zero temperature limit, the CJC embodies a novel quantum anomaly of Goldstone bosons at $\pi$ phase difference which is associated with a $\mathbb{Z}_2$ symmetry at low energies. It can be detected experimentally via an anomalous Fraunhofer pattern.