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Title: Two-band description of resonant superfluidity in atomic Fermi gases

Fermionic superfluidity in atomic Fermi gases across a Feshbach resonance is normally described by the atom-molecule theory, which treats the closed channel as a noninteracting point boson. In this work we present a theoretical description of the resonant superfluidity in analogy to the two-band superconductors. We employ the underlying two-channel scattering model of Feshbach resonance where the closed channel is treated as a composite boson with binding energy ε0 and the resonance is triggered by the microscopic interchannel coupling U12. The binding energy ε0 naturally serves as an energy scale of the system, which has been sent to infinity in the atom-molecule theory. We show that the atom-molecule theory can be viewed as a leading-order low-energy effective theory of the underlying fermionic theory in the limit ε0→∞ and U12→0, while keeping the phenomenological atom-molecule coupling finite. The resulting two-band description of the superfluid state is in analogy to the BCS theory of two-band superconductors. In the dilute limit ε0→∞, the two-band description recovers precisely the atom-molecule theory. The two-band theory provides a natural approach to study the corrections because of a finite binding energy ε0 in realistic experimental systems. For broad and moderate resonances, the correction is not important formore » current experimental densities. However, for extremely narrow resonance, we find that the correction becomes significant. Lastly, the finite binding energy correction could be important for the stability of homogeneous polarized superfluid against phase separation in imbalanced Fermi gases across a narrow Feshbach resonance.« less
Authors:
 [1] ;  [2] ;  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Swinburne Univ. of Technology, Victoria (Australia)
Publication Date:
OSTI Identifier:
1246953
Report Number(s):
LA-UR--14-28538
Journal ID: ISSN 1050-2947; PLRAAN
Grant/Contract Number:
AC02-05CH11231; FT140100003; FT130100815; DP140103231; DP140100637; AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Physical Review. A
Additional Journal Information:
Journal Volume: 91; Journal Issue: 2; Journal ID: ISSN 1050-2947
Publisher:
American Physical Society (APS)
Research Org:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY Feshbach resonance; two-band superconductor; Fermi superfluidity