Suppression of superconductivity due to spin imbalance in Co/Al/Co single electron transistor

TL;DR

This study investigates how spin imbalance in a Co/Al/Co single electron transistor suppresses superconductivity, revealing the interplay between magnetic configurations and superconducting properties.

Contribution

It demonstrates the suppression of superconductivity due to spin imbalance in a ferromagnetic/non-magnetic/ferromagnetic single electron transistor with tunable magnetic states.

Findings

Magnetoresistance of ~100% observed at low bias in superconducting Al state.

Suppression of superconductivity is reduced at high bias and above Al's T_C.

Spin imbalance causes suppression of the superconducting gap in the Al island.

Abstract

Transport properties of ferromagnetic/non-magnetic/ferromagnetic single electron transistors are investigated as a function of external magnetic field, temperature, bias and gate voltage. By designing the magnetic electrodes to have different switching fields, a two-mode device is realized having two stable magnetization states, with the electrodes aligned in parallel and antiparallel. Magnetoresistance of approximately 100% is measured in Co/AlO$_{X}$/Al/AlO$_{X}$/Co double tunnel junction spin valves at low bias, with the Al spacer in the superconducting state. The effect is substantially reduced at high bias and temperatures above the $T_{C}$ of the Al. The experimental results are interpreted as due to spin imbalance of charge carriers resulting in suppression of the superconducting gap of the Al island.