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arXiv 1111.3431cond-mat.supr-concond-mat.quant-gascond-mat.str-el
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Bardeen-Cooper-Schrieffer理论之外的超导性的自洽近似

Self-Consistent Approximations for Superconductivity beyond the Bardeen-Cooper-Schrieffer Theory

Takafumi Kita

摘要:

我们开发了一个简洁的自洽微扰展开超导所有的对过程自然纳入没有绘制“异常”费曼图。这种简化的结果,通过引入一个相互作用的顶点,是对称的,除了普通的空间自旋坐标的粒子-空穴指数。形式主义自动满足守恒定律,包括Luttinger-Ward理论作为正常状态极限,并再现Bardeen-Cooper-Schrieffer理论作为最低阶近似。它使我们能够研究超导体的热力学,单粒子,两粒子,和动力学性质的竞争涨落的基础上的一个单一的功能$Φ[\hat{G}]$的格林函数$\hat{G}$在Nambu空间。具体来说,我们推导出FLEX-S近似的封闭方程,即,涨落交换近似是一种包含所有对过程的超导近似,它除了标准FLEX近似中的那些项外,还包含了额外的项。

英文摘要:

We develop a concise self-consistent perturbation expansion for superconductivity where all the pair processes are naturally incorporated without drawing "anomalous" Feynman diagrams. This simplification results from introducing an interaction vertex that is symmetric in the particle-hole indices besides the ordinary space-spin coordinates. The formalism automatically satisfies conservation laws, includes the Luttinger-Ward theory as the normal-state limit, and reproduces the Bardeen-Cooper-Schrieffer theory as the lowest-order approximation. It enables us to study the thermodynamic, single-particle, two-particle, and dynamical properties of superconductors with competing fluctuations based on a single functional $Φ[\hat{G}]$ of Green's function $\hat{G}$ in the Nambu space. Specifically, we derive closed equations in the FLEX-S approximation, i.e., the fluctuation exchange approximation for superconductivity with all the pair processes, which contains extra terms besides those in the standard FLEX approximation.

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