Phase slip center temperatures attained in superconducting NbTi filaments using an electrical pulse close to T[formula omitted

Abstract

We have investigated the dynamics of dissipative states in NbTi superconducting thin films using electrical step pulse excitations on a sapphire substrate close to Tc. Excitation of a superconducting wire with a current pulse larger than the depairing critical current, Ic, gives rise to a non-equilibrium superconducting state. We identified two dissipative states, the hotspot (HS) and the phase slip center (PSC). Both are signaled by a voltage that emerges after a certain delay time td. We focused on the phase slip phenomenon in the vicinity of Tc and measured the dependence of the delay times on the value of the applied current pulse; these were fitted with the time-dependent Ginzburg-Landau (TDGL) theory due to Tinkham. The film thermal relaxation times were deduced for the phase slip center close to Tc for different samples. In addition, the temperatures at the center of the PSCs were estimated from the blackbody radiation model, and the results are consistent with the PSC formalism.