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arXiv:cond-mat/0610274 · Physical Review A

Single-plane-wave Larkin-Ovchinnikov-Fulde-Ferrell state in BCS-BEC crossover

Yan He, Chih-Chun Chien, Qijin Chen, Kathryn Levin

Published Feb 2, 2007• 35 citations
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Abstract

We study the single-plane-wave Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) states for BCS-Bose-Einstein condensation crossover at general temperatures $T$. Because we include the important effects of noncondensed pairs, our $T\ensuremath{\ne}0$ phase diagrams are different from those reported in earlier work. We find that generalized LOFF phases may be the ground state for a wide range of (weak through moderately strong) interactions, including the unitary regime. However, these LOFF phases are readily destroyed by nonzero $T$.

DOI
10.1103/physreva.75.021602

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We consider a trapped Fermi gas with population imbalance at finite temperatures and map out the detailed phase diagram across a wide Feshbach resonance. We take the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) state into consideration and minimize the thermodynamical potential to ensure stability. Under the local density approximation, we conclude that a stable LOFF state is present only on the BCS side of the Feshbach resonance, but not on the BEC side or at unitarity. Furthermore, even on the BCS side, a LOFF state is restricted at low temperatures and in a small region of the trap, which makes a direct observation of a LOFF state a challenging task.