Microscopic theory of Cooper pair beam splitters based on carbon nanotubes

TL;DR

This paper presents a microscopic analysis of a carbon nanotube-based Cooper pair splitter, showing how efficiency varies with device parameters and can reach nearly 100% in certain non-linear regimes.

Contribution

It provides a detailed microscopic model of Cooper pair splitting in nanotube devices, including effects of geometry, material properties, and spin-orbit scattering, highlighting conditions for optimal efficiency.

Findings

Efficiency limited to 50% in linear regime

Efficiency decays exponentially with superconducting region width

Efficiency can reach nearly 100% in non-linear regime

Abstract

We analyze microscopically a Cooper pair splitting device in which a central superconducting lead is connected to two weakly coupled normal leads through a carbon nanotube. We determine the splitting efficiency at resonance in terms of geometrical and material parameters, including the effect of spin-orbit scattering. While the efficiency in the linear regime is limited to 50% and decay exponentially as a function of the width of the superconducting region we show that it can rise up to $\sim 100%$ in the non-linear regime for certain regions of the stability diagram.