Nonequilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region
Nonequilibrium strong-coupling theory for a driven-dissipative ultracold Fermi gas in the BCS-BEC crossover region
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DOI：
10.1103/physreva.101.013602
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发表时间：
2019-10
影响因子：
2.9
通讯作者：
T. Kawamura;R. Hanai;D. Kagamihara;D. Inotani;Y. Ohashi
中科院分区：
文献类型：
--
作者：
T. Kawamura;R. Hanai;D. Kagamihara;D. Inotani;Y. Ohashi
本文从理论上研究了超冷费米气体在非平衡定态下与两个费米子池耦合的BCS-BEC交叉区的强耦合性质。通过建立一个基于$T$-矩阵近似和Keldysh绿色函数技术的非平衡强耦合理论，我们证明了两个电解液所施加的化学势偏置引起了Fulde-Ferrell-Larkin-Ovchinnikov（FFLO）型对涨落的反常增强（尽管系统没有自旋不平衡），导致BCS-幺正区非平衡超流相变的重入行为。这些配对波动也被发现，有害地增强赝隙现象。由于最近在超冷费米气体中测量到了各种非平衡现象，我们的非平衡强耦合理论将有助于赶上这一研究领域的实验发展。
We theoretically investigate strong-coupling properties of an ultracold Fermi gas in the BCS-BEC crossover regime in the non-equilibrium steady state, being coupled with two fermion baths. By developing a non-equilibrium strong-coupling theory based on the combined $T$-matrix approximation with the Keldysh Green's function technique, we show that the chemical potential bias applied by the two baths gives rise to the anomalous enhancement of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type pairing fluctuations (although the system has no spin imbalance), resulting in the re-entrant behavior of the non-equilibrium superfluid phase transition in the BCS-unitary regime. These pairing fluctuations are also found to anomalously enhance the pseudogap phenomenon. Since various non-equilibrium phenomena have recently been measured in ultracold Fermi gases, our non-equilibrium strong-coupling theory would be useful to catch up this experimental development in this research field.