Valley-Dependent Crossed Andreev Reflection in Graphene/Superconductor/Line-Defect Superlattice Junctions

Abstract

Graphene, a two-dimensional material with remarkable electronic properties, offers significant potential for valley-based electronic devices. In this study, we explore a novel mechanism to achieve valley-dependent, near-perfect crossed Andreev reflection (CAR) in graphene-based junctions by utilizing the valley degree of freedom in a graphene/superconductor/line defect superlattice (LDGSL) structure. The LDGSL introduces unique valley-filtering effects. By incorporating staggered pseudospin potentials and intrinsic spin-orbit coupling in the left graphene electrode, the system selectively enhances CAR for electrons in the K\('\) valley, while simultaneously suppressing local Andreev reflection and elastic cotunneling (ECT). Numerical simulations reveal that CAR is nearly perfect for K\('\) valley electrons with spin-up, while for K valley electrons with spin-down, only ECT is observed. Our results demonstrate the viability of this approach for valley-polarized CAR in graphene/ superconductor junctions, providing a pathway for the development of valley-based quantum information devices.