# Spontaneous charge current in a doped Weyl semimetal

## TL;DR

This paper investigates the conditions under which a doped Weyl semimetal exhibits spontaneous circulating charge currents near its surface, revealing their dependence on doping level and robustness against disorder.

## Contribution

It demonstrates that spontaneous surface charge currents in Weyl semimetals emerge with doping away from the band center and are resilient to weak disorder, expanding understanding of surface transport phenomena.

## Key findings

- No spontaneous current at band center with particle-hole symmetry.
- Surface current appears with doping away from the band center.
- Current direction depends on electron or hole doping.

## Abstract

A Weyl semimetal hosts low-energy chiral surface states, which appear to connect a pair of Weyl nodes in reciprocal space. As these chiral surface states propagate in a given direction, a spontaneous circulating current is expected to appear near the surface of a singly connected Weyl semimetal. This possibility is examined by using a simple model with particle-hole symmetry. It is shown that no spontaneous charge current appears when the Fermi level is located at the band center. However, once the Fermi level deviates from the band center, a spontaneous charge current appears to circulate around the surface of the system and its direction of flow is opposite for the cases of electron doping and hole doping. These features are qualitatively unchanged even in the absence of particle-hole symmetry. The circulating charge current is shown to be robust against weak disorder.