Single-particle properties and pseudogap effects in the BCS-BEC crossover regime of an ultracold Fermi gas above Tc

Shunji Tsuchiya, Ryota Watanabe, Yoji Ohashi

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

We investigate strong-coupling effects on normal-state properties of an ultracold Fermi gas. Within the framework of T -matrix approximation in terms of pairing fluctuations, we calculate the single-particle density of states (DOS), as well as the spectral weight, over the entire BCS-Bose-Einstein condensate (BEC) crossover region above the superfluid phase-transition temperature Tc. Starting from the weak-coupling BCS regime, we show that the so-called pseudogap develops in DOS above Tc, which becomes remarkable in the crossover region. The pseudogap structure continuously changes into a fully gapped one in the strong-coupling BEC regime, where the gap energy is directly related to the binding energy of tightly bound molecules. We determine the pseudogap temperature Tc where the dip structure in DOS vanishes. The value of Tc is shown to be very different from another characteristic temperature T□□ where a BCS-type double-peak structure disappears in the spectral weight. While one finds T□ > □□ in the BCS regime, T□ becomes higher than T□ in the crossover region and BEC regime. Including this, we determine the pseudogap region in the phase diagram of ultracold Fermi gases. Our results would be useful in the search for the pseudogap region in ultracold L6 i and K 40 Fermi gases.

Original languageEnglish
Article number033613
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume80
Issue number3
DOIs
Publication statusPublished - 2009 Sep 16

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Bose-Einstein condensates
crossovers
gases
binding energy
transition temperature
phase diagrams
temperature
approximation
molecules

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Single-particle properties and pseudogap effects in the BCS-BEC crossover regime of an ultracold Fermi gas above Tc. / Tsuchiya, Shunji; Watanabe, Ryota; Ohashi, Yoji.

In: Physical Review A - Atomic, Molecular, and Optical Physics, Vol. 80, No. 3, 033613, 16.09.2009.

Research output: Contribution to journalArticle

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