Pseudogap phenomenon and effects of population imbalance in the normal state of a unitary Fermi gas

Abstract

We investigate strong-coupling corrections to single-particle excitations in the normal state of a spin-polarized unitary Fermi gas. Within the framework of an extended T-matrix approximation, we calculate the single-particle density of states, as well as the single-particle spectral weight, to show that the so-called pseudogap phenomenon gradually disappears with increasing the magnitude of an effective magnetic field. In the highly spin-polarized regime, the calculated spin-polarization rate as a function of the effective magnetic field agrees well with the recent experiment on a 6Li Fermi gas. Although this experiment has been considered to be incompatible with the existence of the pseudogap in an unpolarized Fermi gas, our result clarifies that the observed spin-polarization rate in the highly spin-polarized regime and the pseudogap in the unpolarized limit can be explained in a consistent manner, when one correctly includes effects of population imbalance on single-particle excitations. Since it is a crucial issue to clarify whether the pseudogap exists or not in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas, our results would be useful for the understanding of this strongly interacting fermion system.

17 pages, 7 figures

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Cited by in corpus (8)

• The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems
• Mesoscopic spin transport between strongly interacting Fermi gases
• Strong-coupling corrections to spin susceptibility in the BCS-BEC crossover regime of a superfluid Fermi gas
• Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas
• Triplet pair amplitude in a trapped $s$-wave superfluid Fermi gas with broken spin rotation symmetry
• Spin-dipole mode in a trapped Fermi gas near unitarity
• Anomalous pseudogap in population imbalanced Fermi superfluids
• Triplet pair amplitude in a trapped $s$-wave superfluid Fermi gas with broken spin rotation symmetry. II. Three dimensional continuum case