Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas

Abstract

We theoretically investigate magnetic properties of a trapped ultracold Fermi gas. Including pairing fluctuations within the framework of an extended $T$-matrix approximation (ETMA), as well as effects of a harmonic trap in the local density approximation (LDA), we calculate the local spin susceptibility ${\chi }_{\mathrm{t}}(r,T)$ in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover region. We show that pairing fluctuations cause non-monotonic temperature dependence of ${\chi }_{\mathrm{t}}(r,T)$. Although this behavior looks similar to the spin-gap phenomenon associated with pairing fluctuations in a {\it uniform} Fermi gas, the trapped case is found to also be influenced by the temperature-dependent density profile, in addition to pairing fluctuations. We demonstrate how to remove this extrinsic effect from ${\chi }_{\mathrm{t}}(r,T)$, to study the interesting spin-gap phenomenon purely originating from pairing fluctuations. Since experiments in cold atom physics are always done in a trap, our results would be useful for the assessment of preformed pair scenario, from the viewpoint of spin-gap phenomenon.

25 pages, 10 figures

References in corpus (11)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• Scanning tunneling spectroscopy of high-temperature superconductors
• 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
• Breakdown of Fermi liquid description for strongly interacting fermions
• Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas
• Quantum mechanical limitations to spin diffusion in the unitary Fermi gas
• Thermodynamics of a trapped unitary Fermi gas
• Spin transport in a unitary Fermi gas close to the BCS transition

Cited by in corpus (2)

• Spin Susceptibility Above the Superfluid Onset in Ultracold Fermi Gases
• Spin-dipole mode in a trapped Fermi gas near unitarity