Abstract
We investigate the uniform spin susceptibility in the BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas. Including pairing fluctuations within the framework of an extended -matrix approximation, we show that exhibits nonmonotonic temperature dependence in the normal state. In particular, is suppressed near the superfluid phase transition temperature due to strong pairing fluctuations. To characterize this anomalous behavior, we introduce the spin-gap temperature as the temperature at which takes a maximum value. Determining in the whole BCS-BEC crossover region, we identify the spin-gap regime in the phase diagram of a Fermi gas in terms of the temperature and the strength of a pairing interaction. We also clarify how the spin-gap phenomenon is related to the pseudogap phenomenon appearing in the single-particle density of states. Our results indicate that an ultracold Fermi gas in the BCS-BEC crossover region is a very useful system to examine the pseudogap phenomenon and the spin-gap phenomenon in a unified manner.
2 More- Received 4 December 2013
- Publisher error corrected 19 March 2014
DOI:https://doi.org/10.1103/PhysRevA.89.033617
©2014 American Physical Society
Corrections
19 March 2014