Microwave control of the superconducting proximity effect and minigap in magnetic and normal metals

We demonstrate theoretically that microwave radiation applied to superconducting proximity structures controls the minigap and other spectral features in the density of states of normal and magnetic metals, respectively. Considering both a bilayer and Josephson junction geometry, we show that microwaves with frequency ω qualitatively alters the spectral properties of the system: inducing a series of resonances, controlling the minigap size E(mg), and even replacing the minigap with a strong peak of quasiparticle accumulation at zero energy when ω = E(mg). The interaction between light and Cooper pairs may thus open a route to active control of quantum coherent phenomena in superconducting proximity structures.