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We investigate the competition between
superconductivity and ferromagnetism in ultra-small metallic grains using an effective
Hamiltonian that combines a BCS-like pairing term and a Stoner-like spin exchange term. The presence of spin jumps in the ground-state phase diagram is a unique feature of the coexistence of superconducting and ferromagnetic correlations in a metallic grain. We show that this coexistence regime can be made accessible to experiments by tuning an external Zeeman field [1].
We also study the transport properties of an ensemble of chaotic metallic grains in the Coulomb blockade regime and identify signatures of the
competition between superconductivity and ferromagnetism in the mesoscopic fluctuations of the conductance [2].
[1] S. Schmidt, Y. Alhassid and K. Van Houcke, EPL 80, 47004 (2007). [2] S. Schmidt, Y. Alhassid, preprint (2007) |
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