Pairing in a two-component ultracold Fermi gas: Phases with broken-space symmetries

Journal Article · Fri Jul 15 00:00:00 EDT 2005 · Physical Review. A

DOI:https://doi.org/10.1103/PhysRevA.72.013613· OSTI ID:20718405

Sedrakian, Armen; Muether, Herbert ^[1]; Mur-Petit, Jordi; Polls, Artur ^[2]

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1. Institute for Theoretical Physics, Tuebingen University, D-72076 Tuebingen (Germany)
2. Departament d'Estructura i Constituents de la Materia, Universitat de Barcelona, E-08028 Barcelona (Spain)

We explore the phase diagram of a two-component ultracold atomic Fermi gas interacting with zero-range forces in the limit of weak coupling. We focus on the dependence of the pairing gap and the free energy on the variations in the number densities of the two species while the total density of the system is held fixed. As the density asymmetry is increased, the system exhibits a transition from a homogenous Bardeen-Cooper-Schrieffer (BCS) phase to phases with spontaneously broken global space symmetries. One such realization is the deformed Fermi surface superfluidity (DFS) which exploits the possibility of deforming the Fermi surfaces of the species into ellipsoidal form at zero total momentum of Cooper pairs. The critical asymmetries at which the transition from DFS to the unpaired state occurs are larger than those for the BCS phase. In this precritical region the DFS phase lowers the pairing energy of the asymmetric BCS state. We compare quantitatively the DFS phase to another realization of superconducting phases with broken translational symmetry: the single-plane-wave Larkin-Ovchinnikov-Fulde-Ferrell phase, which is characterized by a nonvanishing center-of-mass momentum of the Cooper pairs. The possibility of the detection of the DFS phase in the time-of-flight experiments is discussed and quantified for the case of {sup 6}Li atoms trapped in two different hyperfine states.

• OSTI ID: 20718405
• Journal Information: Physical Review. A, Vol. 72, Issue 1; Other Information: DOI: 10.1103/PhysRevA.72.013613; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ASYMMETRY
ATOMS
BCS THEORY
COMPARATIVE EVALUATIONS
COOPER PAIRS
COUPLING
DENSITY
FERMI GAS
FERMI LEVEL
FERMIONS
FREE ENERGY
LITHIUM
LITHIUM 6
PAIRING ENERGY
PHASE DIAGRAMS
SUPERFLUIDITY
SYMMETRY
TIME-OF-FLIGHT METHOD
TRAPPING