Interplay between magnetism and superconductivity in a hybrid magnon-photon bilayer system

Spin waves in magnetic films are affected by the vicinity to a superconductor. Here we focus on a bilayer stack made of an insulating Yttrium Iron Garnet (YIG) film and a high-$T_c$ YBCO superconducting planar resonator and report microwave transmission spectra to monitor the temperature evolution of magnon-photon polaritons. We show that the observed temperature dependence of normal mode splitting and frequency shift with respect to the unperturbed magnon mode can be ultimately related to the penetration depth of YBCO, as an effect of the interplay between spin waves and Meissner currents.