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

• Published in: Physica. C, Superconductivity Vol. 589; p. 1
• Main Authors: Harrabi, K., Mekki, A., Bahlouli, H., Mathieu, P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-10-2021; Elsevier BV
• Subjects: Black body radiation; Critical current (superconductivity); Delay time; Excitation; Filaments; Niobium base alloys; Phase transitions; Sapphire; Slip; Substrates; Superconductivity; Thermal relaxation; Thin films; Time dependence
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2021.1353933

•The work presented in this paper is a study of dissipative state in NbTi thin film on a sapphire substrate. In response to an electric step current exceeding the critical current Ic, a voltage appears after a certain delay time td. Near the transition temperature Tc, the type of dissipation was identified as phase slip center. And the delay of nucleation is analyzed according to a Time-Dependent Ginzburg-Landau system of equations, leaving a unique time parameter for fitting: the thermal cooling time of the film on its substrate. Although different, this situation bears similarities with photon detection using a Superconducting Single Photon Detector (SSPD), which implies the formation of a dissipative on the site of absorption; absorption; therefore, its repetition rate performance is limited by the film cooling time (reset time). Moreover, estimation of the temperatures attained in the core of the phase slip center from the blackbody radiation theory of the acoustic phonons revealed that they were larger than to be larger than the substrate temperature and remained below the transition temperature Tc.•Hereby, it is understood that the above-mentioned manuscript has not been published, nor accepted for publication, elsewhere, or under editorial review for publication elsewhere.
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.