Fluctuation Superconductivity in Mesoscopic Aluminum Rings
Nicholas C. Koshnick,1
Hendrik Bluhm,1
Martin E. Huber,2
Kathryn A. Moler1*
Fluctuations are important near phase transitions, where they
can be difficult to describe quantitatively. Superconductivity
in mesoscopic rings is particularly intriguing because the critical
temperature is an oscillatory function of magnetic field. There
is an exact theory for thermal fluctuations in one-dimensional
superconducting rings, which are therefore expected to be an
excellent model system. We measured the susceptibility of many
rings, one ring at a time, by using a scanning superconducting
quantum interference device that can isolate magnetic signals
that are seven orders of magnitude smaller than applied flux.
We find that the fluctuation theory describes the results and
that a single parameter characterizes the ways in which the
fluctuations are especially important at magnetic fields where
the critical temperature is suppressed.
2 Department of Physics, University of Colorado Denver, Denver, CO 80204, USA.
* To whom correspondence should be addressed. E-mail: kmoler{at}stanford.edu
