Nonlocal superconducting correlations in graphene in the quantum Hall regime

TL;DR

This paper investigates nonlocal superconducting correlations in graphene under quantum Hall conditions, revealing that lattice orientation significantly influences crossed Andreev reflection and nonlocal resistance, with interference effects causing oscillations and sign changes.

Contribution

It demonstrates how lattice orientation affects nonlocal superconducting correlations in graphene, highlighting the role of edge types and magnetic field interference effects.

Findings

CAR is small for zigzag edges

CAR can exceed normal transmission for armchair edges

Nonlocal resistance oscillates and changes sign with magnetic field

Abstract

We study Andreev processes and nonlocal transport in a three-terminal graphene-superconductor hybrid system under a quantizing perpendicular magnetic field [G.-H. Lee et al., Nature Phys. 13, 693 (2017)]. We find that the amplitude of the crossed Andreev reflection (CAR) processes crucially depends on the orientation of the lattice. By employing Landauer-B\"{u}ttiker scattering theory, we find that CAR is generally very small for a zigzag edge, while for an armchair edge it can be larger than the normal transmission, thereby resulting in a negative nonlocal resistance. In the case of an armchair edge and with a wide superconducting region (as compared to the superconducting coherence length), CAR exhibits large oscillations as a function of the magnetic field due to interference effects. This results in sign changes of the nonlocal resistance.