Condensed Matter Seminar

Kathryn Moler
Stanford University

Thursday, February 8, 2007
1:00 pm in SPL 52

Fluctuations in Mesoscopic Superconducting Rings

Abstract: We demonstrate a scanning micro-Superconducting QUantum Interference Device (SQUID) that can isolate magnetic signals as small as a few hundred Bohr magnetons in the presence of applied fields that generate up to seven orders of magnitude in background signal. We characterize many individual, small, quasi-one-dimensional aluminum rings, one ring at a time, using the micro-SQUID's ability to probe the weak magnetic response near the onset of superconductivity where fluctuations are important.

Near zero applied field, contrary to earlier results on a single ring, we find agreement with a theoretical framework based on non-Gaussian fluctuations in Ginzburg-Landau theory. At applied magnetic fields where superconductivity should be destroyed due to the Little-Parks effect, we find large fluctuations and show that they can be described by an application of the same theoretical framework.