P-wave Cooper pair splitting

TL;DR

This paper investigates how spin-active interfaces influence Cooper pair splitting in superconductor-ferromagnet devices, revealing new ways to generate p-wave-like entangled states using s-wave superconductors for quantum computing applications.

Contribution

It introduces a theoretical analysis of spin-active scattering effects in Cooper pair splitters, showing how to realize p-wave splitting with s-wave superconductors via spin-flipped crossed Andreev reflection.

Findings

Spin-active interfaces enable p-wave splitting with s-wave superconductors.

New features in conductance and cross correlations due to spin activity.

Access to Bell states beyond typical spin singlet states.

Abstract

Splitting of Cooper pairs has recently been realized experimentally for s-wave Cooper pairs. A split Cooper pair represents an entangled two-electron pair state which has possible application in on-chip quantum computation. Likewise the spin-activity of interfaces in nanoscale tunnel junctions has been investigated theoretically and experimentally in recent years. However, the possible implications of spin-active interfaces in Cooper pair splitters so far have not been investigated. We analyse the current and the cross correlation of currents in a superconductor ferromagnet beamsplitter including spin-active scattering. Using the Hamiltonian formalism we calculate the cumulant generating function of charge transfer. As a first step, we discuss characteristics of the conductance for crossed Andreev reflection in superconductor ferromagnet beamsplitters with s-wave and p-wave superconductors and no spin-active scattering. In a second step, we consider spin-active scattering and show how to realize p-wave splitting only using a s-wave superconductor via the process of spin-flipped crossed Andreev reflection. We present results for the conductance and cross correlations. Spin-activity of interfaces in Cooper pair splitters allows for new features in ordinary s-wave Cooper pair splitters, that can otherwise only be realised by using p-wave superconductors. In particular it provides access to Bell states different from the typical spin singlet state.