High harmonic generation in altermagnets

We study high harmonic generation in altermagnetic metals with and without spin-orbit coupling. The altermagnetism manifests itself in the magnetic field dependence of the low harmonics associated with intraband dynamics. Spin-orbit coupling leads to additional higher-energy peaks and plateau structures originating from interband transitions. While the pure altermagnet or spin-orbit system exhibits no circular dichroism in the high harmonic response, an altermagnetic system with spin-orbit coupling shows such a dichroism. We also analyze the spin currents and their high harmonic spectrum.