When chiral photons meet chiral fermions - Photoinduced anomalous Hall effects in Weyl semimetals

TL;DR

This paper demonstrates that circularly polarized light can induce a Hall effect in Weyl semimetals by shifting Weyl nodes, creating a magnetic-field-free Hall response linked to photon chirality.

Contribution

It reveals a novel photoinduced Hall effect in Weyl semimetals caused by light-driven Weyl node shifts, without external magnetic fields.

Findings

Photoinduced Hall conductivity estimated within experimental range.

Chiral photons cause momentum shifts of Weyl nodes proportional to their chirality.

The effect is applicable to TaAs family of Weyl semimetals.

Abstract

The Weyl semimetal is characterized by three-dimensional linear band touching points called Weyl nodes. These nodes come in pairs with opposite chiralities. We show that the coupling of circularly polarized photons with these chiral electrons generates a Hall conductivity without any applied magnetic field in the plane orthogonal to the light propagation. This phenomenon comes about because with all three Pauli matrices exhausted to form the three-dimensional linear dispersion, the Weyl nodes cannot be gapped. Rather, the net influence of chiral photons is to shift the positions of the Weyl nodes. Interestingly, the momentum shift is tightly correlated with the chirality of the node to produce a net anomalous Hall signal. Application of our proposal to the recently discovered TaAs family of Weyl semimetals leads to an order-of-magnitude estimate of the photoinduced Hall conductivity which is within the experimentally accessible range.