绝热表面间的非绝热转变：超导原子点接触中的相扩散
Nonadiabatic transitions between adiabatic surfaces: phase diffusion in superconducting atomic point contacts
摘要：
受电流偏置超导原子点接触实验的启发，研究了强耗散条件下绝热面间非绝热跃迁的一般问题。对于单沟道器件，超导电流由超导相位差在两个Andreev能级上的扩散运动决定。这些表面仅在低到中等传输的绝热极限中解耦，而对于高传输曲线交叉是重要的。本文从全密度矩阵的一般主方程出发，导出了过阻尼极限下绝热表面上粒子数的近似时间演化方程，由此可得到相应的观测量。原子点接触的情况下的具体结果是在协议与实验观察，不能用传统的理论解释。
英文摘要：
Motivated by experiments with current biased superconducting atomic point contacts the general problem of nonadiabatic transitions between adiabatic surfaces in presence of strong dissipation is studied. For a single channel device the supercurrent is determined by the diffusive motion of the superconducting phase difference on two Andreev levels. These surfaces are uncoupled only in the adiabatic limit of low to moderate transmissions, while for high transmissions curve crossings are important. Starting from a general master equation of the full density matrix an approximate time evolution equation for the populations on the adiabatic surfaces in the overdamped limit is derived from which the relevant observables can be obtained. Specific results for the case of atomic point contacts are in agreement with experimental observations that cannot be explained by conventional theory.
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