Excitation properties and effects of mass imbalance in the BCS-BEC crossover regime of an ultracold Fermi gas

Abstract

We investigate single-particle properties of a mass-imbalanced Fermi gas in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover region. In the presence of mass imbalance, we point out that the ordinary $T$-matrix approximation, which has been extensively used to clarify various BCS-BEC crossover physics in the mass-balanced case, unphysically gives a double-valued solution in terms of the superfluid phase transition temperature $T_{\mathrm{c}}$ in the crossover region. To overcome this serious problem, we include higher order strong-coupling corrections beyond the $T$-matrix level. Using this extended $T$-matrix theory, we calculate single-particle excitations in the normal state above $T_{\mathrm{c}}$. The so-called pseudogap phenomena originating from pairing fluctuations are shown to be different between the light mass component and heavy mass component, which becomes more remarkable at higher temperatures. Since Fermi condensates with hetero-Cooper pairs have recently been discussed in various fields, such as exciton (polariton) condensates, as well as color superconductivity, our results would be useful for the further development of Fermi superfluid physics, beyond the conventional superfluid state with homo-Cooper pairs.

26 pages, 14 figures

References in corpus (27)

• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• 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
• Ultracold Fermionic Feshbach Molecules of ${}^{23}$Na${}^{40}$K
• BEC-BCS crossover, phase transitions and phase separation in polarized resonantly-paired superfluids
• Ultracold Heteronuclear Fermi-Fermi Molecules
• Quantum phases of a Two-Dimensional Dipolar Fermi Gas
• Two-species fermion mixtures with population imbalance
• Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas
• Formation of Ultracold Fermionic NaLi Feshbach Molecules
• Fermion Superfluids of Non-Zero Orbital Angular Momentum near Resonance
• Transition to a Bose-Einstein condensate of excitons at sub-Kelvin temperatures
• Polarized Fermi condensates with unequal masses: Tuning the tricritical point
• Pseudo-gap pairing in ultracold Fermi atoms
• Strongly-resonant p-wave superfluids
• BCS-BEC crossover in an asymmetric two-component Fermi gas
• Enhanced paraconductivity-like fluctuations in the radio frequency spectra of ultracold Fermi atoms
• All-optical production of a degenerate mixture of 6Li and 40K and creation of heteronuclear molecules
• Resonant pairing between Fermions with unequal masses
• Spin susceptibility and fluctuation corrections in the BCS-BEC crossover regime of an ultracold Fermi gas
• 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 (13)

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• Dynamical instability of a driven-dissipative electron-hole condensate in the BCS-BEC-crossover region
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• Strong-coupling corrections to spin susceptibility in the BCS-BEC crossover regime of a superfluid Fermi gas
• Beyond-mean-field description of a trapped unitary Fermi gas with mass and population imbalance
• Hetero pairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with mass imbalance
• Pseudogap phenomenon and effects of population imbalance in the normal state of a unitary Fermi gas
• Thermal transitions, pseudogap behavior and BCS-BEC crossover in Fermi-Fermi mixtures
• Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas
• Pauli limited d-wave superconductors: Quantum breached pair phase and thermal transitions
• Triplet pair amplitude in a trapped $s$-wave superfluid Fermi gas with broken spin rotation symmetry
• Triplet pair amplitude in a trapped $s$-wave superfluid Fermi gas with broken spin rotation symmetry. II. Three dimensional continuum case
• Interplay of mass imbalance and frustration in correlated band insulators