Hetero pairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with mass imbalance

Abstract

We investigate the superfluid phase transition and single-particle excitations in the BCS (Bareen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas with mass imbalance. In our recent paper [R. Hanai, et. al., Phys. Rev. A 88, 053621 (2013)], 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 $T_{\mathrm{c}}$ in the presence of mass imbalance. However, at the same time, the ETMA was also found to give the vanishing $T_{\mathrm{c}}$ 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 $T_{\mathrm{c}}$ 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 the light component and heavy component. We also point out that a ${}^6$Li-${}^{40}$K mixture is a useful system for the realization of a hetero pairing state, as well as for the study of component-dependent pseudogap phenomena.

27 pages, 14 figures

References in corpus (28)

• Spin-Injection Spectroscopy of a Spin-Orbit Coupled Fermi Gas
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions
• Thermodynamics of the BCS-BEC crossover
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Exploring an ultracold Fermi-Fermi mixture: Interspecies Feshbach resonances and scattering properties of 6Li and 40K
• Quantum degenerate two-species Fermi-Fermi mixture coexisting with a Bose-Einstein condensate
• BEC-BCS crossover, phase transitions and phase separation in polarized resonantly-paired superfluids
• Ultracold Heteronuclear Fermi-Fermi Molecules
• Determination of the Fermion Pair Size in a Resonantly Interacting Superfluid
• Two-species fermion mixtures with population imbalance
• Fermion Superfluids of Non-Zero Orbital Angular Momentum near Resonance
• Transition to a Bose-Einstein condensate of excitons at sub-Kelvin temperatures
• Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas
• Polarized Fermi condensates with unequal masses: Tuning the tricritical point
• Pseudo-gap pairing in ultracold Fermi atoms
• Quantum mechanical limitations to spin diffusion in the unitary Fermi gas
• Strongly-resonant p-wave superfluids
• Heavy-Light Fermion Mixtures at Unitarity
• All-optical production of a degenerate mixture of 6Li and 40K and creation of heteronuclear molecules
• Resonant pairing between Fermions with unequal masses
• Mixtures of ultracold fermions with unequal masses
• Superfluid shells for trapped fermions with mass and population imbalance
• Superfluid pairing between fermions with unequal masses
• Asymmetric Fermi superfluid with different atomic species in a harmonic trap
• Low temperature properties of the fermionic mixtures with mass imbalance in optical lattice

Cited by in corpus (5)

• Beyond-mean-field description of a trapped unitary Fermi gas with mass and population imbalance
• Pauli limited d-wave superconductors: Quantum breached pair phase and thermal transitions
• Mass-Imbalanced Superconductivity in Effective Two-Channel Kondo Lattice
• Triplet pair amplitude in a trapped $s$-wave superfluid Fermi gas with broken spin rotation symmetry. II. Three dimensional continuum case
• Interplay of the pseudogap and the BCS gap for heteropairs in ${}^{40}$K-${}^6$Li mixture