Giant inverse Faraday effect in Dirac semimetals

TL;DR

This paper reports a giant inverse Faraday effect in Dirac semimetals, where circularly polarized light induces a large effective magnetic field, enabling strong light-spin interactions and potential spintronic applications.

Contribution

It demonstrates a significantly enhanced inverse Faraday effect in Dirac semimetals due to their unique electronic properties, which was not previously observed.

Findings

HDP increases with film thickness and saturates.

Sign change of HDP with carrier type transition.

Peak HDP near charge neutrality point.

Abstract

We have studied helicity dependent photocurrent (HDP) in Bi-based Dirac semimetal thin films. HDP increases with film thickness before it saturates, changes its sign when the majority carrier type is changed from electrons to holes and takes a sharp peak when the Fermi level lies near the charge neutrality point. These results suggest that irradiation of circularly polarized light to Dirac semimetals induces an effective magnetic field that aligns the carrier spin along the light spin angular momentum and generates a spin current along the film normal. The effective magnetic field is estimated to be orders of magnitude larger than that caused by the inverse Faraday effect (IFE) in typical transition metals. We consider the small effective mass and the large $g$-factor, characteristics of Dirac semimetals with strong spin orbit coupling, are responsible for the giant IFE, opening pathways to develop systems with strong light-spin coupling.