Coexistence of superfluid gap and pseudogap in the BCS-BEC crossover regime of a trapped Fermi gas below Tc

Ryota Watanabe, Shunji Tsuchiya, Yoji Ohashi

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Abstract

We investigate strong pairing fluctuations and effects of a harmonic trap in the superfluid phase of an ultracold Fermi gas. Including amplitude and phase fluctuations of the inhomogeneous superfluid order parameter Δ(r) in a trap within a combined T-matrix theory with the local density approximation, we examine local properties of single-particle excitations and a thermodynamic quantity in the BCS-BEC crossover region. Below the superfluid phase transition temperature Tc, we show that inhomogeneous pairing fluctuations lead to a shell structure of the gas cloud in which the spatial region where the ordinary BCS-type superfluid density of states appears surrounded by the region where the pseudogap associated with strong pairing fluctuations dominates single-particle excitations. The former spatial region enlarges to eventually cover the whole gas cloud far below Tc. We also examine how this shell structure affects the photoemission spectrum, as well as the local pressure. Since a cold Fermi gas is always trapped in a harmonic potential, our results would be useful for the study of strong-coupling superfluid physics, including this realistic situation.

Original languageEnglish
Article number063603
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume86
Issue number6
DOIs
Publication statusPublished - 2012 Dec 4

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ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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