Ultrafast Mimic of Spin Hall Effect in Altermagnets

The spin Hall effect, a key effect in creating spin currents and controlling magnetic order at the nanoscale, presupposes a population of mobile carriers in a conducting state, in which a driving charge current generates a perpendicular spin-current. Here we show an ultrafast light-wave driven spin Hall analogue exists in altermagnetic semiconductors and insulators, in which a laser pulse generates both a charge current and a co-occurring perpendicular pure spin current. Employing the example of the theoretically predicted 2d altermagnetic Lieb-lattice semiconductor Cr2SO, we demonstrate that pulse design allows lightwave control over the postpulse spin/charge current ratio ξres, with values exceeding unity obtained in the multicycle regime. Our findings thus both considerably broaden the materials base for spin Hall/spin splitter physics, as well as establishing 2d altermagnets as a platform providing a new route for valleytronic lightwave control of spin- and charge currents at ultrafast times.