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
@article{arxiv.cond-mat/0309055,
title = {Giant fluctuations of superconducting order parameter in Ferromagnet/superconductor single electron transistors},
author = {J. Johansson and V. Korenivski and D. B. Haviland and A. Brataas},
journal= {arXiv preprint arXiv:cond-mat/0309055},
year = {2009}
}