Chiral magnetic effect in the absence of Weyl node

TL;DR

This paper demonstrates that the chiral magnetic effect can occur without Weyl nodes, relying instead on Berry curvature, thus broadening the range of materials where CME might be observed.

Contribution

It reveals that the CME does not require Weyl nodes, challenging the conventional understanding that links CME solely to Weyl semimetals.

Findings

CME can occur without Weyl nodes due to Berry curvature effects.

Weyl nodes are essential for the chiral anomaly but not for CME.

Nodeless CME may be observed in metallic quantum anomalous Hall insulators.

Abstract

The nodal points in a Weyl semimetal are generally considered as the causes of the chiral anomaly and the chiral magnetic effect (CME). Employing a linear-response analysis of a two-band lattice model, we show that the Weyl nodes and thus the chirality are not required for the CME, while they remain crucial for the chiral anomaly. Similar to the anomalous Hall effect, the CME results directly from the Berry curvature of energy bands, even when there is no monopole source from the Weyl nodes. Therefore, the phenomenon of the CME could be observed in a wider class of materials. Motivated by this result, we suggest that the nodeless CME may appear in three-dimensional quantum anomalous Hall insulators, but after they become metallic due to the band deformation caused by inversion symmetry breaking.