Scanning SQUID investigation of the suppression of superfluid density in mesoscopic superconducting rings

ORAL

Abstract

We use a scanning SQUID microscope to measure the suppression of the superconducting response of quasi-1D rings specifically designed to exhibit phase winding fluctuations below Tc.~ Extremely high flux sensitivity as well as a positionable sensor capable of measuring many individual rings and subtracting the background in situ make scanning SQUID ideal for this measurement.~ The physical ring parameters are carefully controlled during fabrication to reduce the ring's superconducting phase stiffness by tuning the energy spacing of states where a uniform phase winds an integer number of times around the ring.~ When the energy difference between adjacent phase winding states is approximately equal to the temperature, the superfluid density is suppressed by the contribution of multiple states to the response. ~ We present susceptibility data and a theoretical framework that demonstrate how these fluxoid fluctuations suppress the ring's diamagnetism below Tc.

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Authors

  • Julie A. Bert

    • Stanford University

  • Nicholas C. Koshnick

    • Stanford University

  • Hendrik Bluhm

    • Stanford Univeristy
    • Harvard University

  • Martin E. Huber

    • Departments of Physics and Electrical Engineering, University of Colorado Denver, Denver, Colorado, 80217, USA.
    • University of Colorado Denver

  • Kathryn A. Moler

    • Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
    • Stanford University