Pseudodiffusive conduction at the Dirac point of a normal-superconductor junction in graphene

A. R. Akhmerov; C. W. J. Beenakker

doi:10.1103/PhysRevB.75.045426

← Back to search

Pseudodiffusive conduction at the Dirac point of a normal-superconductor junction in graphene

A. R. Akhmerov, C. W. J. Beenakker

DOI 10.1103/PhysRevB.75.045426 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

A ballistic strip of graphene (width W⪢length L) connecting two normal metal contacts is known to have a minimum conductivity of 4e2∕πh at the Dirac point of charge neutrality. We calculate what happens if one of the two contacts becomes superconducting. While the ballistic conductance away from the Dirac point is increased by Andreev reflection at the normal-superconductor (NS) interface, we find that the minimum conductivity stays the same. This is explained as a manifestation of pseudodiffusive conduction at the Dirac point. As a generalization of our results for a ballistic system, we provide a relation between the conductance GNS of an arbitrarily disordered normal-superconductor junction in graphene and its value GN when both contacts are in the normal state.