Light-induced anomalous Hall conductivity in massive 3D Dirac semimetal Co$_3$Sn$_2$S$_2$

TL;DR

This study demonstrates that circularly polarized light can induce a transition from a massive 3D Dirac semimetal to a Weyl semimetal by generating Berry curvature, as evidenced by measured anomalous Hall conductivity in Co$_3$Sn$_2$S$_2$.

Contribution

It provides experimental evidence for Floquet theory predictions of Dirac-Weyl conversion in massive Dirac semimetals using ultrafast spectroscopy.

Findings

CPL induces measurable anomalous Hall conductivity in Co$_3$Sn$_2$S$_2$

The Dirac band splitting reaches about 60% of the mass gap

The observed AHC matches theoretical predictions based on Berry curvature

Abstract

Weyl semimetals can emerge from Dirac semimetals when the time-reversal or spatial-inversion symmetries are broken. Recently, it has been proposed based on the Floquet theory that Dirac semimetals can be converted into Weyl semimetals even by shining circularly polarized light (CPL). Here we have investigated the possibility of such a Dirac-Weyl conversion by measuring the CPL-induced anomalous Hall conductivity (AHC) in a massive 3D Dirac semimetal Co$_3$Sn$_2$S$_2$ in the paramagnetic phase using ultrafast mid-infrared pump-terahertz Faraday rotation probe spectroscopy. We find that the field-strength and driving frequency dependence of the observed AHC is well accounted for by CPL-induced nonzero Berry curvature associated with the splitting of the Dirac bands as predicted by the Floquet theory. The estimated splitting of the Dirac bands reaches about 60 % of the mass gap and the calculated CPL-induced AHC quantitatively reproduces the experimental observation, demonstrating a promising route toward the realization of Floquet-Weyl states from massive Dirac semimetals.