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arXiv 0801.1743cond-mat.str-elcond-mat.supr-conhep-phnucl-th
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粒子数不平衡费米气体的温度效应

Temperature Effects in a Fermi Gas with Population Imbalance

Heron Caldas, A. L. Mota

摘要:

研究了自旋布居不平衡的费米气体中的温度效应。从热隙方程的一般表达式中,我们发现,在{ \it弱耦合极限}中,转变温度$T_c$作为两种粒子之间的化学势和质量不对称性的各种可能性的函数的解析表达式。在一定的非对称范围内,该方程对$T_c$总是有两个解,这被解释为一种重入现象或温度效应引起的配对。我们表明,较低的$T_c$是从来没有一个稳定的解决方案。在{ \it强耦合极限}中也得到了同样的结果。仔细分析了系统的势能,避免了对不稳定解的考虑。我们还得到了三临界点的化学势和质量不平衡的情况下,超过这些点,我们适当地减少热力学势找到稳定和亚稳的一级过渡线。

英文摘要:

We investigate temperature effects in a Fermi gas with imbalanced spin populations. From the general expression of the thermal gap equation we find, in {\it weak coupling limit}, an analytical expression for the transition temperature $T_c$ as a function of various possibilities of chemical potential and mass asymmetries between the two particle species. For a range of asymmetry between certain specific values, this equation always has two solutions for $T_c$ which has been interpreted as a reentrant phenomena or a pairing induced by temperature effect. We show that the lower $T_c$ is never related to a stable solution. The same results are obtained in {\it strong coupling limit}. The thermodynamical potential is carefully analyzed to avoid the consideration of the unstable solutions. We also obtain the tricritical points for the chemical potential and mass imbalanced cases, and beyond these points we properly minimize the thermodynamic potential to find the stable and metastable first order transition lines.

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