Moving flux quanta cool superconductors by a microwave breath

Abstract

Abstract Almost any use of a superconductor implies a non-equilibrium state. Remarkably, while a sufficiently high-power electromagnetic field of GHz frequency can stimulate superconductivity, fast motion of magnetic flux quanta (Abrikosov vortices) can trigger an instability abruptly quenching the superconducting state. Here, we show that such dynamical quenching of the vortex state in Nb thin films can be advanced or delayed by tuning the power and frequency of the microwave ac stimulus added to a dc bias current. The experimental findings are supported by time-dependent Ginzburg-Landau simulations and they can be explained, qualitatively, based on a model of “breathing mobile hot spots”, implying a competition of heating and cooling of quasiparticles along the trajectories of moving fluxons whose core sizes vary in time. In addition, we demonstrate universality of the stimulation effect on the thermodynamic and transport properties of type II superconductors.