Giant fluctuations of superconducting order parameter in Ferromagnet/superconductor single electron transistors

TL;DR

This paper theoretically investigates spin-dependent transport in ferromagnet/superconductor/ferromagnet single electron transistors, revealing significant gap dependence on magnetic states and predicting large magneto-resistance and fluctuations in superconducting order due to spin accumulation.

Contribution

It introduces a comprehensive theoretical model accounting for spin accumulation, relaxation, gap suppression, and charging effects in such transistors, highlighting the impact on superconducting fluctuations.

Findings

Gap strongly depends on magnetic state, causing large magneto-resistance.

Spin accumulation fluctuations can induce the superconducting island to fluctuate.

Negative magneto-resistance of up to 100% observed.

Abstract

Spin dependent transport in a ferromagnet/superconductor/ferromagnet single electron transistor is studied theoretically with spin accumulation, spin relaxation, gap suppression, and charging effects taken into account. A strong dependence of the gap on the magnetic state of the outer electrodes is found, which gives rise to a negative magneto-resistance of up to 100 %. We predict that fluctuations of the spin accumulation due to tunneling of quasi-particles can play such an important role as to cause the island to fluctuate between the superconducting