Abstract
Superconducting rings represent an ideal system for studying phase coherence in one dimension. We study the temperature dependence of the magnetic susceptibility of superconducting rings with a scanning superconducting quantum interference device. The physical parameters of the rings were designed to reduce the superconducting phase stiffness. We observe a suppression of the susceptibility signal below the critical temperature, which we attribute to a thermodynamic sampling of metastable states with different phase winding number, termed fluxoid fluctuations. We introduce a simple model (N. C. Koshnick, Ph.D. thesis, Stanford University, 2009) for the susceptibility of a ring affected by fluxoid fluctuations and compare it with one-dimensional (1D) Ginzburg-Landau (GL) theory including all thermal fluctuations. We find good agreement between our fluxoid model and the full 1D GL theory up to a shift in the critical temperature. Additionally, our magnetic susceptibility data are well described by 1D GL theory.
- Received 27 August 2010
DOI:https://doi.org/10.1103/PhysRevB.84.134523
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