Phase slip center temperatures attained in superconducting NbTi filaments using an electrical pulse close to T_c

We have investigated the dynamics of dissipative states in NbTi superconducting thin films using electrical step pulse excitations on a sapphire substrate close to T_c. Excitation of a superconducting wire with a current pulse larger than the depairing critical current, I_c, 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 t_d. We focused on the phase slip phenomenon in the vicinity of T_c 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 T_c 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.