Spin-polarized transport in F/S nanojunctions

We study spin-dependent electronic transport across ferromagnet/superconductor ballistic junctions modeled using tight-binding Hamiltonians with s, p and d orbitals and material-specific parameters. The first result of this paper is that, by accurately modeling the band structure of the bulk materials, one can reproduce the measured differential conductance of Cu/Pb nanocontacts1,2. In contrast the differential conductance of CO/Pb contacts can only be reproduced if an enhanced magnetic moment is present at the interface. The second result concerns the reliability of a method proposed in Refs. 1-3 for determining the degree of polarization of a ferromagnet. By fitting the material-specific differential conductance curves to curves calculated using a single-band model we show that this method does not yield reliable values for polarization and spin-dependent transmission.