Chiral gauge field in light-driven Dirac electrons in Co₃Sn₂S₂

Floquet engineering has been proposed as an intriguing approach to control topological materials such as Dirac semimetals and Weyl semimetals using light. It was proposed based on Floquet theory that a chiral gauge field can be implemented to Dirac electrons by a circularly polarized periodic driving field, and the transition from Dirac semimetal to Weyl semimetal can be achieved. We experimentally found that Co₃Sn₂S₂ in the paramagnetic phase, which is a 3D Dirac electron system, exhibited an instantaneous anomalous Hall effect when irradiated with a mid-infrared circularly polarized light pulse. We quantitatively compared the intensity and frequency dependences of the observed anomalous Hall conductivity with the effective model describing the Floquet state of Co₃Sn₂S₂, suggesting that the nonzero Berry curvature due to light-induced chiral gauge field causes the anomalous Hall effect. Our demonstration paves a new pathway for ultrafast manipulation of topological phases of matter and for further exploring various topological phases achievable only by light.