Coherent charge transport through an interface between a superconductor and hopping insulator: Role of barrier properties

M. Kirkengen; J. Bergli; Y. M. Galperin

doi:10.1103/PhysRevB.74.195321

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Coherent charge transport through an interface between a superconductor and hopping insulator: Role of barrier properties

M. Kirkengen, J. Bergli, Y. M. Galperin

DOI 10.1103/PhysRevB.74.195321 · Physical Review B

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Abstract

At low temperatures and voltages tunneling transport through an interface between a superconductor and hopping insulator is dominated by coherent two-electron tunneling between the Cooper-pair condensate and pairs of localized states [Kozub et al., Phys. Rev. Lett. 96, 107004 (2006)]. By detailed analysis of such transport we show that the interface resistance is extremely sensitive to the properties of the tunneling barriers, as well as to the asymptotic behavior of the localized states. In particular, a dramatic cancellation takes place for hydrogenlike impurities and ideal barriers. However, some disorder can lift the cancellations, restoring the interface transport. We also study the non-Ohmic behavior of the interface resistor and show that it is sensitive to the Coulomb correlation of the occupation probabilities of the involved localized states. It is expected that the non-Ohmic contribution to the I−V curve will experience pronounced mesoscopic (fingerprint) fluctuations.