Special Condensed Matter Physics Seminar

Note Special Time and Place!
10:30 a.m., Monday, February 9, 2004
Room 2202, Physics Building

From ultracold superfluids to high temperature superconductors

Jelena Stajic

(University of Chicago)

Abstract: Most systems which exhibit superfluidity can be described well by either Bardeen-Cooper-Schrieffer (BCS) theory (e.g. conventional superconductors) or Bose-Einstein condensation (BEC, e.g. ⁴He). High temperature superconductors (HTS) are believed by some to fall in between these two extremes since their coherence length is considerably shorter compared to conventional superconductors. Here we show how a theory of crossover between the BCS and BEC limits, capable of explaining some of the exotic properties of HTS, can be derived by extending Hartree approximated time dependent Ginzburg-Landau theory (TDGL) to arbitrary coupling strength. This crossover theory is then generalized and applied to a different physical system -- the ultracold Fermi gas near a Feshbach resonance, in which the coupling strength can be tuned by the magnetic field. Superfluidity in these systems was observed only recently by the experimental groups at JILA and Innsbruck, in ⁴⁰K and ⁶Li respectively. Critical temperature in the crossover region is computed for a range of parameters and possible signatures of the superfluid transition are analyzed.

Host: Das Sarma
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