论文标题
无序超导体的理论，适用于非线性电流响应
Theory of Disordered Superconductors with Applications to Nonlinear Current Response
论文作者
论文摘要
我介绍了由Eilenberger，Larkin和Ovchinnikov和Eliashberg开发的准经典传输方程，对超导合金的理论和基本方程式的综述。该公式是Landau正常费米液体理论的自然延伸，以与强相关金属的超导状态。对于肮脏的金属，传输方程将电荷扩散的方程式减少，而低温下的Drude电导率给出了电流响应。强烈无序金属对超导状态的电荷和电流响应的扩散方程的扩展延伸得出了非平衡的准经典Keldysh传播器的USADEL方程。讨论了USADEL方程的适用性条件，疾病对当前响应的成对效应，包括在肮脏极限下对EM场的非线性电流响应，$τ\ ll \ hbar/δ$。显示出相同的非线性导致光子产生的源电流和非线性KERR旋转，这是由多模式EM场对超导体激发的非线性响应驱动的。简要讨论了非线性源电流与SRF腔的潜在相关性作为轴突样候选物的检测器。
I present a review of the theory and basic equations for charge transport in superconducting alloys starting from the Keldysh formulation of the quasiclassical transport equations developed by Eilenberger, Larkin and Ovchinnikov and Eliashberg. This formulation is the natural extension of Landau's theory of normal Fermi liquids to the superconducting state of strongly correlated metals. For dirty metals the transport equations reduce to equations for charge diffusion, with the current response given by the Drude conductivity at low temperatures. The extension of the diffusion equation for the charge and current response of a strongly disordered normal metal to the superconducting state yields Usadel's equations for the non-equilibrium quasiclassical Keldysh propagator. The conditions for the applicability of the Usadel equations are discussed, the pair-breaking effect of disorder on the current response, including the nonlinear current response to an EM field in the dirty limit, $τ\ll \hbar/Δ$, are reported. The same nonlinearity is shown to lead to source currents for photon generation and nonlinear Kerr rotation driven by the nonlinear response to excitation of the superconductor by a multi-mode EM field. The potential relevance of the nonlinear source currents to SRF cavities as detectors of axion-like dark matter candidates is briefly discussed.
