TY - JOUR

T1 - Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

AU - Hanai, Ryo

AU - Ohashi, Yoji

N1 - Publisher Copyright:
© 2014 American Physical Society.

PY - 2014/10/21

Y1 - 2014/10/21

N2 - We investigate the superfluid phase transition and single-particle excitations in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an unpolarized ultracold Fermi gas with mass imbalance (where two different species contributing to Cooper pairs have different atomic masses). In our recent paper [R. Hanai, Phys. Rev. A 88, 053621 (2013)PLRAAN1050-294710.1103/PhysRevA.88.053621], we showed that an extended T-matrix approximation (ETMA) can overcome the serious problem known in the ordinary (non-self-consistent) T-matrix approximation that it unphysically gives double-valued superfluid phase transition temperature Tc in the presence of mass imbalance. However, at the same time, the ETMA was also found to give the vanishing Tc in the weak-coupling and highly mass-imbalanced case. In this paper, we inspect the correctness of this ETMA result, using the self-consistent T-matrix approximation (SCTMA). We show that the vanishing Tc is an artifact of the ETMA, coming from an internal inconsistency of this theory. The superfluid phase transition actually always occurs, irrespective of the ratio of mass imbalance. We also apply the SCTMA to the pseudogap problem in a mass-imbalanced Fermi gas. We show that pairing fluctuations induce different pseudogap phenomena between the light component and heavy component. We also point out that a Li6-K40 mixture is a useful system for the realization of a heteropairing state, as well as for the study of component-dependent pseudogap phenomena.

AB - We investigate the superfluid phase transition and single-particle excitations in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an unpolarized ultracold Fermi gas with mass imbalance (where two different species contributing to Cooper pairs have different atomic masses). In our recent paper [R. Hanai, Phys. Rev. A 88, 053621 (2013)PLRAAN1050-294710.1103/PhysRevA.88.053621], we showed that an extended T-matrix approximation (ETMA) can overcome the serious problem known in the ordinary (non-self-consistent) T-matrix approximation that it unphysically gives double-valued superfluid phase transition temperature Tc in the presence of mass imbalance. However, at the same time, the ETMA was also found to give the vanishing Tc in the weak-coupling and highly mass-imbalanced case. In this paper, we inspect the correctness of this ETMA result, using the self-consistent T-matrix approximation (SCTMA). We show that the vanishing Tc is an artifact of the ETMA, coming from an internal inconsistency of this theory. The superfluid phase transition actually always occurs, irrespective of the ratio of mass imbalance. We also apply the SCTMA to the pseudogap problem in a mass-imbalanced Fermi gas. We show that pairing fluctuations induce different pseudogap phenomena between the light component and heavy component. We also point out that a Li6-K40 mixture is a useful system for the realization of a heteropairing state, as well as for the study of component-dependent pseudogap phenomena.

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U2 - 10.1103/PhysRevA.90.043622

DO - 10.1103/PhysRevA.90.043622

M3 - Article

AN - SCOPUS:84908102343

SN - 1050-2947

VL - 90

JO - Physical Review A - Atomic, Molecular, and Optical Physics

JF - Physical Review A - Atomic, Molecular, and Optical Physics

IS - 4

M1 - 043622

ER -