BCS-BEC crossover in 2D Fermi gases with Rashba spin-orbit coupling.
BCS-BEC crossover in 2D Fermi gases with Rashba spin-orbit coupling.
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DOI：
10.1103/physrevlett.108.145302
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发表时间：
2011-09
影响因子：
8.6
通讯作者：
Lianyi He;Xu-Guang Huang
中科院分区：
文献类型：
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作者：
Lianyi He;Xu-Guang Huang
本文对具有Rashba自旋轨道耦合（SOC）的二维费米气体中的BCS-BEC交叉进行了系统的理论研究。通过在存在有吸引力的短程相互作用的情况下解决精确的两体问题，我们表明SOC增强了束缚态的形成：束缚态的结合能E（B）和有效质量m（B）沿着SOC的增大而增大。对于多体问题，即使在弱吸引下，当SOC变得与费米动量相当时，稀释的费米气体可以从BCS超流体状态演化为分子的玻色凝聚。研究了基态性质和Berezinskiii-Kosterlitz-BKT转变温度，得到了不同极限下的解析结果。对于大SOC，BKT转变温度恢复到具有有效质量m（B）的玻色气体的转变温度。我们发现，在SOC存在的情况下，凝聚态和超流密度具有不同的行为：由于分子结合力的增加，凝聚态密度通常会被SOC增强;由于分子有效质量m（B）的非平凡性，超流密度被抑制。
We present a systematic theoretical study of the BCS-BEC crossover in two-dimensional Fermi gases with Rashba spin-orbit coupling (SOC). By solving the exact two-body problem in the presence of an attractive short-range interaction we show that the SOC enhances the formation of the bound state: the binding energy E(B) and effective mass m(B) of the bound state grows along with the increase of the SOC. For the many-body problem, even at weak attraction, a dilute Fermi gas can evolve from a BCS superfluid state to a Bose condensation of molecules when the SOC becomes comparable to the Fermi momentum. The ground-state properties and the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature are studied, and analytical results are obtained in various limits. For large SOC, the BKT transition temperature recovers that for a Bose gas with an effective mass m(B). We find that the condensate and superfluid densities have distinct behaviors in the presence of SOC: the condensate density is generally enhanced by the SOC due to the increase of the molecule binding; the superfluid density is suppressed because of the nontrivial molecule effective mass m(B).