Spin Current in Junctions composed of Multi-band Superconductors with a Spin-density Wave

TL;DR

This paper investigates spin currents in multi-band superconductor junctions with spin-density waves, revealing mechanisms to control spin and charge currents for potential spintronics applications.

Contribution

It introduces a model demonstrating the control of spin and charge currents in superconductor junctions with spin-density waves, highlighting a method to switch off charge current while maintaining spin current.

Findings

Finite spin current can flow without charge current.

Josephson current can be switched off independently.

Spin current is proportional to Josephson current, enabling measurement.

Abstract

We calculate a nondissipative spin current and show that it can flow with or without a charge current. We consider a two-band model which can be applied to the description of Fe-based pnictides in coexistence regime of superconductivity and spin-density wave. Using quasiclassical Green's functions approach and tunneling Hamiltonian method we show that there exists a possibility to switch off the Josephson current while leaving the spin current finite. Moreover, it is possible to have the critical Josephson current and the critical spin current being proportional to each other, thus giving a possibility to measure the spin current via the Josephson current. The underlying mechanism is the interfering hopping of electron--hole pairs between different bands of the superconductors composing the junction. This is an intrinsic property of the system and provides a unique and natural way to utilize junctions made solely of pnictides in promising applications in spintronics devices.