All-optical generation of antiferromagnetic magnon currents via the magnon circular photogalvanic effect

The creation and control of spin currents at the nanoscale are key goals in spintronics and magnonics. One of the most promising approaches is to use optical means for spin current generation and control. Importantly, this would allow one to adapt concepts from photocurrent generation in electronic systems, in particular the circular photogalvanic effect. The CPGE holds great promise for functionality and applications since it allows to selectively generate currents and probe wavefunction quantum geometry only on the surface. We here introduce the magnon circular photogalvanic effect (MCPGE) as enabled by two-magnon Raman scattering. We show that a circularly polarized laser drive generates a magnon current whose strength and direction are controllable through the angle of incidence and polarization via the MCPGE. This magnonic photocurrent is predicted to lead to an inverse spin Hall voltage of experimentally accessible values in platinum contacts, with a characteristic angle dependence, enabling the experimental verification of both the magnon current generation and the underlying MCPGE with existing technology. The MCPGE as proposed in this work is the leading contribution to magnon photocurrents in antiferromagnetic insulators.