Thermo dynamic properties of spin-orbit-coupled two-dimensional Fermi gases
Received date: 2019-05-05
Online published: 2019-12-31
应用平均场理论研究自旋轨道耦合和塞曼场共同作用下二维费米气体的热力学性质. 通过求解能隙方程和粒子数方程, 讨论了自旋轨道耦合和塞曼场对系统的等温压缩系数、压强、超流序参和热力学熵的影响, 发现了不同于三维系统的新性质. 研究表明: 在自旋轨道耦合和塞曼场共同作用下, 玻色-爱因斯坦凝聚(Bose-Einstein condensate, BEC)极限区域的等温压缩系数和压强基本不随相互作用变化, 这与三维系统中等温压缩系数和压强在 BEC 极限区域随相互作用强度线性改变明显不同; 在 BCS(Bardeen, Cooper and Schrieffer) 极限下, 等温压缩系数和压强敏感地依赖于体系的自旋轨道耦合强度和塞曼场强度. 在合适的参数区域, 等温压缩系数、压强、超流序参数和热力学熵随自旋轨道耦合和 塞曼场强度非单调的变化行为; 在有限温度下, 热力学熵随自旋轨道耦合和塞曼场的改变在正常相和超流相表现出完全相反的变化规律.
梁成功, 张云波 . 自旋轨道耦合二维费米气体的热力学性质[J]. 上海大学学报(自然科学版), 2019 , 25(6) : 914 -923 . DOI: 10.12066/j.issn.1007-2861.2150
Using the mean-field theory, we investigate the thermodynamic properties of two-dimensional Fermi gases with spin-orbit coupling and Zeeman field. By solving the gap and particle-number equations, we discuss the influences of spin-orbit coupling and Zeeman field on the isothermal compressibility, pressure, superfluid order parameter and entropy, and find some anomalous behaviors different from the three-dimensional systems. It is indicated that due to the influences of spin-orbit coupling and Zeeman field, the isothermal compressibility and the pressure do not change with the interatomic interactions in the Bose-Einstein condensate (BEC) limits, which is distinctly different from the case of three-dimensional systems, where these two thermodynamic quantities change linearly with the interactions. In the Bardeen, Cooper and Schrieffer (BCS) limits, the isothermal compressibility and the pressure sensitively depends on the strengths of spin-orbit coupling and Zeeman field. In appropriate parameters, by adjusting the spin-orbit coupling and the Zeeman field we also observe non-monotonic changes of the isothermal compressibility, pressure, superfluid order parameter and entropy. In addition, it is found that the spin-orbit coupling and the Zeeman field leads to opposite changes of the entropy between the normal phase and the superfluid phase.
Key words： spin-orbit coupling; superfluid; isothermal compressibility; entropy; pressure
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