Spin susceptibility and effects of inhomogeneous strong pairing fluctuations in a trapped ultracold Fermi gas

Abstract

We theoretically investigate magnetic properties of a unitary Fermi gas in a harmonic trap. Including strong pairing fluctuations within the framework of an extended $T$-matrix approximation (ETMA), as well as effects of a trap potential within the local density approximation (LDA), we calculate the local spin susceptibility $\chi (T,r)$ above the superfluid phase transition temperature $T_{\mathrm{c}}$. We show that the formation of preformed singlet Cooper pairs anomalously suppresses $\chi (T,r)$ in the trap center near $T_{\mathrm{c}}$. We also point out that, in the unitarity limit, the spin-gap temperature in a uniform Fermi gas can be evaluated from the observation of the spatial variation of $\chi (T,r)$. Since a real ultracold Fermi gas is always in a trap potential, our results would be useful for the study of how this spatial inhomogeneity affects thermodynamic properties of an ultracold Fermi gas in the BCS-BEC crossover region.

7 pages, 3 figures, Proceedings of QFS2015

References in corpus (11)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• Resonantly-paired fermionic superfluids
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• Quantum mechanical limitations to spin diffusion in the unitary Fermi gas
• Cooper pairing above the critical temperature in a unitary Fermi gas
• Uniform spin susceptibility and spin-gap phenomenon in the BCS-BEC crossover regime of an ultracold Fermi gas