Non-BCS superfluidity in trapped ultracold Fermi gases

Journal Article · Sat Sep 15 04:00:00 EDT 2007 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.76.033620· OSTI ID:21020570

Jensen, L M; Kinnunen, J; Toermae, P ^[1]

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1. Department of Physics, Nanoscience Center, P.O. Box 35, FIN-40014 University of Jyvaekylae, Jyvaekylae (Finland)

Superconductivity and superfluidity of fermions require, within the BCS theory, matching of the Fermi energies of the two interacting Fermion species. Difference in the number densities of the two species leads either to a normal state, to phase separation, or - potentially - to exotic forms of superfluidity such as Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, Sarma state, or breached pair state. We consider ultracold Fermi gases with polarization, i.e., spin-density imbalance. We show that, due to the gases being trapped and isolated from the environment in terms of particle exchange, exotic forms of superfluidity appear as a shell around the Bardeen-Cooper-Schrieffer (BCS) superfluid core of the gas and, for large density imbalance, in the core as well. We obtain these results by describing the effect of the trapping potential by using the Bogoliubov-de Gennes equations. For comparison to experiments, we calculate also the condensate fraction, and show that, in the center of the trap, a polarized superfluid leads to a small dip in the central density difference. We compare the results to those given by local density approximation and find qualitatively different behavior.

• OSTI ID: 21020570
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 3 Vol. 76; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
APPROXIMATIONS
BCS THEORY
COMPARATIVE EVALUATIONS
CONDENSATES
DENSITY
FERMI GAS
FERMIONS
GASES
PARTICLES
POLARIZATION
POTENTIALS
SPIN
SUPERCONDUCTIVITY
SUPERFLUIDITY
TEMPERATURE RANGE 0000-0013 K
TRAPPING
TRAPS