Microscopic theory of Cooper pair beam splitters based on carbon nanotubes

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 decays exponentially as a function of the width of the superconducting region, we show that it can rise to $\ensuremath{\sim}$$100%$ in the nonlinear regime for certain regions of the stability diagram.