Strong-coupling limit of Eliashberg theory.
Strong-coupling limit of Eliashberg theory.
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Eliashberg 理论的强耦合极限。
DOI：
10.1103/physrevb.51.11625
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
R. Combescot
中科院分区：
文献类型：
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作者：
R. Combescot
我们研究了Eliashberg超导理论的强耦合极限，与典型的声子能量相比，耦合强度为无穷大，临界温度变大。这一极限是有意义的，因为它既普遍又简单，我们希望从这项研究中对传统的超导强耦合机制有更深的了解。我们在这个问题上的工作既是解析的，也是数值的。在T=0时，我们发现激发谱是离散的。我们在物理上将激发态解释为由于一种极化子效应而产生的束束态。我们证明了完全在实频率轴上工作，就可以从本质上解析地求解Eliashberg方程。在有限温度下，我们发现了T=0结构的热涂抹。由于临界温度与零温差相比较小，热效应可以看作是几乎所有温度范围内的一种微扰。本着这种精神，我们给出了一个简单的近似解，几乎定量地再现了精确的数值结果。
We study the strong-coupling limit of the Eliashberg theory of superconductivity, where the coupling strength \ensuremath{\lambda} goes to infinity and the critical temperature gets large compared to a typical phonon energy. This limit is of interest because it is both universal and simple, and we may hope to obtain from this study a deeper understanding of the conventional strong-coupling regime of superconductivity. Our work on this problem is both analytical and numerical. At T=0, we find that the excitation spectrum is discrete. We interpret physically the excited states as bound states due to a type of polaronic effect. We show that one can solve the Eliashberg equations essentially analytically by working fully on the real frequency axis. At finite temperature we find a thermal smearing of the T=0 structure. Since the critical temperature is small compared to the zero-temperature gap, thermal effects can be treated as a kind of perturbation over almost all the temperature range. In this spirit, we give a simple approximate solution which reproduces almost quantitatively the exact numerical results.