Strong-coupling corrections to spin susceptibility in the BCS-BEC crossover regime of a superfluid Fermi gas

Abstract

We theoretically investigate the uniform spin susceptibility $\chi$ in the superfluid phase of an ultracold Fermi gas in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover region. In our previous paper [H. Tajima, {\it et. al.}, Phys. Rev. A {\bf 89}, 033617 (2014)], including pairing fluctuations within an extended $T$-matrix approximation (ETMA), we showed that strong pairing fluctuations cause the so-called spin-gap phenomenon, where $\chi$ is anomalously suppressed even in the normal state near the superfluid phase transition temperature $T_{\mathrm{c}}$. In this paper, we extend this work to the superfluid phase below $T_{\mathrm{c}}$, to clarify how this many-body phenomenon is affected by the superfluid order. From the comparison of the ETMA $\chi$ with the Yosida function describing the spin susceptibility in a weak-coupling BCS superfluid, we identify the region where pairing fluctuations crucially affect this magnetic quantity below $T_{\mathrm{c}}$ in the phase diagram with respect to the strength of a pairing interaction and the temperature. This spin-gap regime is found to be consistent with the previous pseudogap regime determined from the pseudogapped density of states. We also compare our results with a recent experiment on a ${}^6$Li Fermi gas. Since the spin susceptibility is sensitive to the formation of spin-singlet preformed pairs, our results would be useful for the study of pseudogap physics in an ultracold Fermi gas on the viewpoint of the spin degrees of freedom.

24 pages, 8 figures

References in corpus (27)

• 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
• Magnetic order in the pseudogap phase of high-$T_C$ superconductors
• Resonantly-paired fermionic superfluids
• 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
• Measurement of the Entropy and Critical Temperature of a Strongly Interacting Fermi Gas
• BCS-BEC crossover at finite temperature in the broken-symmetry phase
• Evolution of the Normal State of a Strongly Interacting Fermi Gas from a Pseudogap Phase to a Molecular Bose Gas
• Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$
• Coexistence of competing orders with two energy gaps in real and momentum space in high-Tc superconductor Bi2Sr2-xLaxCuO6+delta
• Breakdown of Fermi liquid description for strongly interacting fermions
• Speckle Imaging of Spin Fluctuations in a Strongly Interacting Fermi Gas
• Pseudo-gap pairing in ultracold Fermi atoms
• Quantum mechanical limitations to spin diffusion in the unitary Fermi gas
• BCS-BEC crossover in an asymmetric two-component Fermi gas
• Cooper pairing above the critical temperature in a unitary Fermi gas
• Unitary Fermi gas at finite temperature in the epsilon expansion
• Phase structure of spin-imbalanced unitary Fermi gases
• Uniform spin susceptibility and spin-gap phenomenon in the BCS-BEC crossover regime of an ultracold Fermi gas
• Polarized Fermi gases at finite temperature in the BCS-BEC crossover
• Hetero pairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with mass imbalance
• Spin transport in a unitary Fermi gas close to the BCS transition

Cited by in corpus (15)

• Exploring the ferromagnetic behaviour of a repulsive Fermi gas via spin dynamics
• Pseudogaps in strongly interacting Fermi gases
• Ground-state thermodynamic quantities of homogeneous spin-$1/2$ fermions from the BCS region to the unitarity limit
• Many Fermi polarons at nonzero temperature
• Strong-coupling corrections to ground-state properties of a superfluid Fermi gas
• Thermal crossover, transition, and coexistence in Fermi polaronic spectroscopies
• Pairing correlations across the superfluid phase transition in the unitary Fermi gas
• Emergence of a pseudogap in the BCS-BEC crossover
• Mesoscopic spin transport between strongly interacting Fermi gases
• Precursor of Superfluidity in a Strongly Interacting Fermi Gas with Negative Effective Range
• Weak-coupling to unitarity crossover in Bose-Fermi mixtures: Mixing-demixing and spontaneous symmetry breaking in trapped systems
• Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas
• Spin-dipole mode in a trapped Fermi gas near unitarity
• Finite-range effect in the two-dimensional density-induced BCS-BEC crossover
• Interplay of the pseudogap and the BCS gap for heteropairs in ${}^{40}$K-${}^6$Li mixture