由于同步Andreev和逆Andreev反射引起的高透明正常超导分束器中的正电流互相关
Positive current cross-correlations in a highly transparent normal-superconducting beam splitter due to synchronized Andreev and inverse Andreev reflections
摘要：
建立了对称偏置三端正常金属-超导体-正常金属（NSN）器件中线性微分电流-电流互相关dSab/dV的预测。高度透明的接触变得特别有趣，因为它们具有正的dSab/dV。在高透明度下，基于交叉Andreev反射（CAR）的过程对电流和dSab/dV的贡献可以忽略不计。在这种情况下，电流-电流的互相关可以解释为两个NS界面之间的相干耦合，其形式为同步Andreev反射和逆Andreev反射，对应于一对类电子准粒子和一对类空穴准粒子从正常电极到达超导体并在超导体中湮灭的过程。因此，正的dSab/dV并不自动意味着CAR。对于隧道接触，由于CAR，dSab/dV为正。在这两个极端之间，在中间的振幅，dSab/dV是负的，因为导致正相关的两个过程，只发生在小幅度。我们使用散射理论来获得电流和噪声的解析表达式，并使用紧束缚模型进行微观计算，以获得对物理过程的清晰解释。
英文摘要：
Predictions are established for linear differential current-current cross-correlations dSab/dV in a symmetrically biased three-terminal normal metal-superconductor-normal metal (NSN) device. Highly transparent contacts turn out to be especially interesting because they feature positive dSab/dV. At high transparency, processes based on Crossed Andreev Reflection (CAR) contribute only negligibly to the current and to dSab/dV. Under these circumstances, current-current cross-correlations can be plausibly interpreted as a coherent coupling between the two NS interfaces in the form of synchronized Andreev and inverse Andreev reflections, corresponding to the process where a pair of electron-like quasi-particles and a pair of hole-like quasi-particles arrive from the normal electrodes and annihilate in the superconductor. Hence, positive dSab/dV does not automatically imply CAR. For tunnel contacts, dSab/dV is positive because of CAR. In between these two extremities, at intermediate transparencies, dSab/dV is negative because both processes which cause positive correlations, occur only with small amplitude. We use scattering theory to obtain analytic expressions for current and noise, and microscopic calculation using a tight binding model in order to obtain a clear interpretation of the physical processes.
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