非对准约瑟夫森结中的φ态和反夫琅和费花样
φ-State and Inverted Fraunhofer Pattern in Nonaligned Josephson Junctions
摘要：
从理论上研究了一般非对准约瑟夫森结在外加磁场作用下的特性，揭示了一种与磁通量有关的电流-相位关系。我们解释了异常CPR的起源，通过外部场诱导的电流密度流内的二维准经典Keldysh-Usadel框架。特别地，证明了非对准的约瑟夫森结可以用于获得不同于0和π的基态，对应于所谓的φ结，其通过外部磁通量是可调谐的。此外，我们表明，标准的夫琅和费中心峰的临界超电流可能会被反转成一个局部极小值，仅仅是由于在平面结的几何因素。这与最近的实验测量显示出这种令人困惑的特征具有很好的一致性[R。S. Keizer等人，Nature 439，825（2006）]。
英文摘要：
A generic nonaligned Josephson junction in the presence of an external magnetic field is theoretically considered and an unusual flux-dependent current-phase relation (CPR) is revealed. We explain the origin of the anomalous CPR via the current density flow induced by the external field within a two-dimensional quasiclassical Keldysh-Usadel framework. In particular, it is demonstrated that nonaligned Josephson junctions can be utilized to obtain a ground-state other than 0 and π, corresponding to a so-called φ-junction, which is tunable via the external magnetic flux. Furthermore, we show that the standard Fraunhofer central peak of the critical supercurrent may be inverted into a local minimum solely due to geometrical factors in planar junctions. This yields good consistency with a recent experimental measurement displaying such type of puzzling feature [R. S. Keizer et al, Nature 439, 825 (2006)].
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