Cavity-Mediated Superconductor–Ferromagnet Interaction

We present a microscopic, perturbative theoretical analysis of interactions between a ferromagnetic (FM) and a superconducting (SC) monolayer mediated by photons in a cavity. This facilitates interactions over macroscopic distances, in contrast with extensively researched FM–SC proximity systems, and ensures there is no interfacial suppression of their respective order parameters. Specifically, we deduce the anisotropy field induced across the FM due to the presence of the SC when the system is subjected to a symmetry-breaking external field. Other quantities such as renormalized dispersion relations can also be deduced. The model is a modification and quantum mechanical extension of the principle presented in PRB 102, 180506(R), 2020. Their separation means the FM and SC may be held at different temperatures, suggesting a potential application as a bridge in spintronic–superconducting circuitry.