Valley-based Cooper Pair Splitting via Topologically Confined Channels in Bilayer Graphene

TL;DR

This paper demonstrates a novel valley-based Cooper pair splitting mechanism in bilayer graphene, leveraging topologically confined channels at domain walls, which enables entangled electron pairs without Coulomb interaction or energy filtering.

Contribution

It introduces a kinetic Cooper pair splitting method using valley-chiral modes in bilayer graphene, derived from an effective model and analyzing conductance from local Andreev reflections.

Findings

Valley-chiral modes enable Cooper pair splitting in bilayer graphene.

Conductance analysis shows dominance of local Andreev reflection.

Crossed Andreev reflection is absent in this setup.

Abstract

Bilayer graphene hosts valley-chiral one dimensional modes at domain walls between regions of different interlayer potential or stacking order. When such a channel is brought into proximity to a superconductor, the two electrons of a Cooper pair which tunnel into it move in opposite directions because they belong to different valleys related by the time-reversal symmetry. This is a kinetic variant of Cooper pair splitting, which requires neither Coulomb repulsion nor energy filtering but is enforced by the robustness of the valley isospin in the absence of atomic-scale defects. We derive an effective model for the guided modes in proximity to an s-wave superconductor, calculate the conductance carried by split and spin-entangled electron pairs, and interpret it as a result of local Andreev reflection processes, whereas crossed Andreev reflection is absent.