Mesoscopic proximity effect probed through superconducting tunneling contacts

Abstract

We investigate the properties of complex mesoscopic superconducting-normal hybrid devices, Andreev Interferometers in the case where the current is probed through a superconducting tunneling contact whereas the proximity effect is generated by a transparent SN interface. We show within the quasiclassical Green’s-functions technique, how the fundamental SNIS element of such structures can be mapped onto an effective S′IS junction, where S′ is the proximized material with an effective energy gap Eg<Δ. The conductance through such a sample at T=0 vanishes if V<Δ+Eg, whereas at T>0 the conductance shows a peak at V=Δ−Eg. We propose the Andreev interferometer, where Eg can be tuned by an external phase φ and displays maxima at 0 mod 2π and minima at π mod 2π. This leads to peculiar current-phase relations, which depart from a zero-phase maximum or minimum depending on the bias voltage and can even show intermediate extreme at V≈Δ. We propose an experiment to verify our predictions and show how our results are consistent with recent, unexplained experimental results.

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