Theory of superfluids with population imbalance: Finite-temperature and BCS-BEC crossover effects

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.75.014521· OSTI ID:20976642

Qijin, Chen; Yan, He; Chien, C -C; Levin, K ^[1]

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1. James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

In this paper we present a very general theoretical framework for addressing fermionic superfluids over the entire range of BCS to Bose Einstein condensation (BEC) crossover in the presence of population imbalance or spin polarization. Our emphasis is on providing a theory which reduces to the standard zero temperature mean-field theories in the literature, but necessarily includes pairing fluctuation effects at nonzero temperature within a consistent framework. Physically, these effects are associated with the presence of preformed pairs (or a fermionic pseudogap) in the normal phase, and pair excitations of the condensate, in the superfluid phase. We show how this finite T theory of fermionic pair condensates bears many similarities to the condensation of point bosons. In the process we examine three different types of condensate: the usual breached pair or Sarma phase and both the one- and two-plane-wave Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states. The last of these has been discussed in the literature albeit only within a Landau-Ginzburg formalism, generally valid near T{sub c}. Here we show how to arrive at the two-plane-wave LOFF state in the ground state as well as at general temperature T.

• OSTI ID: 20976642
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 1 Vol. 75; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BCS THEORY
BOSE-EINSTEIN CONDENSATION
BOSONS
CONDENSATES
EXCITATION
FERMIONS
FLUCTUATIONS
GROUND STATES
MEAN-FIELD THEORY
SPIN ORIENTATION
SUPERFLUIDITY
TEMPERATURE DEPENDENCE
WAVE PROPAGATION