Microwave Kerr/Faraday Resonance in Two-dimensional Chiral Superconductors

We investigate the polar Kerr and Faraday effects in two-dimensional multiband chiral superconductors. We show that the clapping modes–the relative phase and amplitude oscillations between two chiral components of the superconducting order parameter–lie well within the quasiparticle excitation gap in multiband systems and dominate these magneto-optical responses in the microwave regime. The Kerr and Faraday rotation angles exhibit the resonant enhancement with sign reversals in the microwave regime as a function of the light frequency, reaching peak values on the order of 100 nrad–10 $\mu$rad in thin films of candidate chiral superconductors. These resonances are accessible in superconducting atomic layer materials and provide a generic probe of chiral superconductivity in two-dimensional systems.