Critical Phase-Transition Current in Niobium Nitride Thin Films

Abstract—The effect of current and magnetic field on the transition to the superconducting state in niobium nitride thin films has been studied. The critical current dependences of the films on the temperature and magnetic field in the transition region have been determined. Within the framework of models of a normal domain and quasiparticle heating during viscous flow of a magnetic flux, the functional dependences of the critical current have been determined in close vicinity of the superconducting transition temperature. Using the theory of electron heating, we have determined the time of the electron energy relaxation. We also estimated the electron-phonon and the electron-electron inelastic scattering times, the diffusion coefficient of electrons, and heat transfer coefficient.