Terahertz anomalous Hall effect in a Weyl antiferromagnet Mn₃Sn

Antiferromagnetic spin motion at terahertz (THz) frequencies has attracts interests for fast spintronics, but their small responses to external field due to the small net magnetization has inhibited device application. Recently the noncollinear antiferromagnet Mn₃Sn was reported to show large anomalous Hall effect at room temperature comparable to ferromagnets. Here we study the dynamical aspect of the large AHE in Mn₃Sn thin films by using polarization-resolved THz spectroscopy. The THz anomalous Hall conductivity was observed with dissipation-less feature up to 1 THz and peculiar temperature dependence corresponding to the breaking/recovery of symmetry in the spin texture. Observation of the THz anomalous Hall effect demonstrates the ultrafast readout for the antiferromagnetic spintronics using Mn₃Sn and opens a new avenue for studying nonequilibrium dynamics in Weyl antiferromagnets. (author)