Resonant spin transport through a superconducting double barrier structure

TL;DR

This paper investigates resonant electron and hole transport in a superconducting double barrier system, revealing a unique T=1/4 resonance that can generate pure spin currents due to interference effects.

Contribution

It introduces a novel T=1/4 resonance in superconducting double barriers caused by electron-hole interference, differing from normal systems.

Findings

Discovery of T=1/4 resonance due to electron-hole interference

Resonance enables pure spin current generation

Contrast with standard T=1 resonance in normal barriers

Abstract

We study resonant transport through a superconducting double barrier structure. At each barrier, due to the proximity effect, an incident electron can either reflect as an electron or a hole (Andreev reflection). Similarly, transport across the barrier can occur via direct tunneling as electrons as well as via the crossed Andreev channel, where a hole is transmitted. In the subgap regime, for a symmetric double barrier system (with low transparency for each barrier), we find a new T=1/4 resonance (T is the transmission probability for electrons incident on the double barrier structure) due to interference between electron and hole wave-functions between the two barriers, in contrast to a normal double barrier system which has the standard transmission resonance at T=1. We also point out as an application that the resonant value of T=1/4 can produce pure spin current through the superconducting double barrier structure.