Spin can be generated from light. Important mechanisms for this light-spin conversion are the inverse Faraday effect, optical orientation, and optical spin-orbit torque. Previously, these effects were mostly studied in insulators. Recently, we found these effects in the metallic system. Especially, employing the ultrafast timescale of light, we can generate ultrafast dynamics of magnetization.
There is a direct interaction between light and magnetization. One famous example is the magneto-optic Faraday effect. Faraday effect is widely used for an optical instrument, such as optical isolator. We found the inverse Faraday effect in metallic ferromagnets. The circularly polarized light can induce a field-like torque on the magnetization of ferromagnets.
Related works:
Optical-helicity-driven magnetization dynamics: https://www.nature.com/articles/ncomms15085
Field-like torque by inverse Faraday effect: https://doi.org/10.1016/j.jmmm.2018.10.117
Angular momentum of photons can be converted to spin of electrons in semiconductors, such as GaAs. We found that this photon-spin conversion can occur in non-magnetic metals, such as Pt. When the generated spin is transferred to ferromagnets and induces torque, which we call optical spin-orbit torque.
Related works:
Optical spin-orbit torque: https://doi.org/10.1038/s41467-020-15247-3
Coherent excitation of spin waves: https://doi.org/10.1103/PhysRevB.102.014437
Charge current can be generated by injecting light (photons) into the magnetic system. In this case, the magnitude and direction of the photo-current are determined by magnetization. The important mechanism is the spin-orbit coupling, Berry phase, and topological effect.
