Chiral anomaly in Weyl semimetals from spin current injection

TL;DR

This paper reveals a novel topological chiral anomaly in Weyl semimetals induced by spin current injection, leading to unique measurable effects like parallel charge currents and resonant injection signals, expanding understanding of their topological properties.

Contribution

It introduces a new mechanism of chiral anomaly in Weyl semimetals driven by spin current injection, distinct from the traditional electric-magnetic field scenario.

Findings

Detection of electric charge current parallel to magnetic field without electric field

Observation of a sharp resonant peak in injection current

Topological protection of the spin field source in Weyl cones

Abstract

Weyl semimetals are well-known for hosting topologically protected linear band crossings, serving as the analog of the relativistic Weyl Fermions in the condensed matter context. Such analogy persists deeply, allowing the existence of the chiral anomaly under parallel electric and magnetic field in Weyl semimetals. Different from such picture, here we show that, a unique mechanism of the chiral anomaly exists in Weyl semimetals by injecting a spin current with parallel spin polarization and flow direction. The existence of such a chiral anomaly is protected by the topological feature that each Weyl cone can also be a source or drain of the spin field in the momentum space. It leads to measurable experimental signals, such as an electric charge current parallel with an applied magnetic field in the absence of the electric field, and a sharp peak at certain resonant frequency in the injection current in achiral Weyl semimetals through the circular photogalvanic effect. Our work shows that the topological implication of Weyl semimetals goes beyond the link with relativistic Weyl Fermions, and offers a promising scenario to examine the interplay between topology and spin.