Influence of photon-assisted tunneling on heat flow in a normal metal-superconductor tunnel junction

We have investigated theoretically the influence of an ac drive on heat transport in a hybrid normal metal-superconductor tunnel junction in the photon-assisted tunneling regime. We find that the useful heat flux out from the normal metal is always reduced as compared to its magnitude under the static and quasistatic drive conditions. Our results are useful to predict the operative conditions of ac-driven superconducting electron refrigerators.