Measurement of the gap relaxation time of superconducting NbTi strips on a sapphire substrate

K. Harrabi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


We report on the study of the transient voltage response of superconducting NbTi strips to an over-critical current pulse (I> Ic, where Ic is the pair-breaking current). In this experiment, a localized normal spot appeared for a current amplitude larger than the critical current. The induced metastable superconducting state was identified as either a hotspot or phase-slip center. These two dissipative modes share the feature of the voltage response occurring after a delay time td, a solution of the time-dependent Ginzburg–Landau (TDGL) theory developed by M. Tinkham. The gap relaxation time was subsequently deduced from fitting the experimental data with the TDGL theory. An agreement was found by choosing an effective gap relaxation time τΔ=4.75ns for a thickness of 50 nm. Assuming the proportionality to sample thickness, this indicates a thermal relaxation time of 96 ps/nm for a NbTi film sputtered at room temperature on polished crystalline Al 2O 3. If we assume that the electron and the phonon specific heats have the same ratio as for pure Nb, then it results in a phonon heat escape time τes/d=32ps/nm.

Original languageEnglish
Article number751
JournalApplied Physics A: Materials Science and Processing
Issue number11
StatePublished - 1 Nov 2019

Bibliographical note

Funding Information:
K. H. gratefully acknowledges the support of the King Fahd University of Petroleum and Minerals, Saudi Arabia, under the SB181006 DSR project. We would like to thank J. P. Maneval for useful discussions.

Publisher Copyright:
© 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

ASJC Scopus subject areas

  • Chemistry (all)
  • Materials Science (all)


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