Determining the temperature-dependent London penetration depth in HTS thin films and its effect on SQUID performance

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Keenan, Shane and Pegrum, Colin and Gali Labarias, Marc and Mitchell, Emma E. (2021) Determining the temperature-dependent London penetration depth in HTS thin films and its effect on SQUID performance. Applied Physics Letters, 119 (14). 142601. ISSN 0003-6951 (https://doi.org/10.1063/5.0065790)

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Abstract

The optimum design of high-sensitivity Superconducting Quantum Interference Devices (SQUIDs) and other devices based on thin high-temperature superconductor (HTS) films requires accurate inductance modeling. This needs the London penetration depth λ to be well defined, not only at 77K, but also for any operating temperature, given the increasingly widespread use of miniature low-noise single-stage cryocoolers. Temperature significantly affects all inductances in any active superconducting device, and cooling below 77 K can greatly improve device performance; however, accurate data for the temperature dependence of inductance and λT for HTS devices are largely missing in the literature. We report here inductance measurements on a set of 20 different thin-film YBa 2Cu 3O 7−x SQUIDs at 77K with thickness t=220 or 113nm. By combining experimental data and inductance modeling, we find an average penetration depth λ 77=nm at 77K, which was independent of t. Using the same methods, we derive an empirical expression for λ for a further three SQUIDs measured on a cryocooler from 50 to 79=K. Our measured value of λ7 and our inductance extraction procedures were then used to estimate the inductances and the effective areas of directly coupled SQUID magnetometers with large washer-style pickup loops. The latter agrees better than 7% with experimentally measured values, validating our measured value of λ and our inductance extraction methods.

  • Item type:Article
    ID code:78154
    Dates:
    Date
    Event
    4 October 2021
    Published
    17 September 2021
    Accepted
    5 August 2021
    Submitted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:14 Oct 2021 08:31
    Last modified:05 Dec 2024 01:19
    URI:https://strathprints.strath.ac.uk/id/eprint/78154
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