Shining light on spintronics: From the spin Hall effect to a novel interaction between light and spins

The magnetic component of light is usually neglected when considering light-matter interactions. This is because the force that acts on the dipoles which originates from the electrical field is orders of magnitude stronger than the Lorentz force. On the other hand, for typical fields, ferromagnetic resonance (FMR) typically on Gigahertz timescales. Therefore, it seems unlikely that optical magnetic fields that oscillate at ∼ 400 − 800 THz may interact with magnetic moments. However, by combining principles from quantum optics, we have recently realized that the equations governing the FMR experiment are relevant even for magnetic fields that oscillate much faster, at optical frequencies. Namely, the interaction between optical beams and the magnetization is made possible.

In this talk, I will walk through the journey that ultimately led us to these conclusions. I will conclude by presenting the optical Hall effect technique which is a sensitive magneto-optical Kerr effect method applicable to nonmagnetic materials, and demonstrate clear imprints of the interaction between light and spins.

References

Assouline et al., Physical Review Research 6, 013012 (2024).

Am-Shalom et al., Nature Communications 16, 6423 (2025).