Spin-gap phenomenon in a strongly interacting ultracold Fermi gas

27th International Conference on Low Temperature Physics

Tajima, H.^1 ; Hanai, R.^1 ; Ohashi, Y.^1

Department of Physics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Kanagawa, Yokohama

223-8522, Japan^1

关键词: BCS-BEC crossover;    Fermi gas;    Finite density;    Normal state;    Pairing fluctuations;    Spin susceptibility;    Superfluid phase;    Ultra-cold;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/568/1/012019/pdf
DOI  :  10.1088/1742-6596/568/1/012019

来源: IOP

【 摘 要 】

We investigate magnetic properties of a strongly interacting ultracold Fermi gas. Within the framework of an extended T-matrix approximation, we calculate the spin susceptibility χ in the unitarity limit. We show that effects of pairing fluctuations on this magnetic quantity are quite different in between the normal state and the superfluid phase. In the normal state, pairing fluctuations cause spin-gap phenomenon near the superfluid phase transition temperature Tc, where χ is anomalously suppressed. In the superfluid phase, on the other hand, the ordinary suppression of χ by the BCS energy gap is weakened by pairing fluctuations, because they induce finite density of states inside the gap. Our results indicate that the spin susceptibility is a useful quantity for the study of pairing fluctuations in the BCS-BEC crossover regime of an ultracold Fermi gas.