Helicity-Dependent Terahertz Emission from a Weyl Semimetal Mn3Sn

In this work, we present the experimental observation of helicity-dependent ultrafast photocurrents in a Mn3Sn film using optical pump-Terahertz emission spectroscopy. The magnitude and direction of photocurrents depend on the polarisation of the pump pulse and the optical incidence angle, but have no dependence on the magnetic field. We combine experimental results with a thorough symmetry analysis to argue that the helicity-dependent photocurrents arise predominantly from the circular photon drag effect.