title: Symmetry-derived half-metallicity in atomic and molecular junctions.
abstract: Achieving highly spin-polarized electric currents in atomic-scale junctions is of great importance in the field of nanoelectronics and spintronics. Based on robust symmetry considerations, we propose a mechanism to block completely one of spin conduction channels for a broad class of atomic and molecular junctions bridging two ferromagnetic electrodes. This particular behavior is due to the wave function orthogonality between spin up s-like states in ferromagnetic electrode and available π channels in the junction. As a consequence, the system would ideally yield 100% spin-polarized current, with a junction acting thus as a "half-metallic" conductor. Using ab initio electron transport calculations, we demonstrate this principle on two examples: (i) a short carbon chain and (ii) a π-conjugated molecule (polythiophene) connected either to model semi-infinite Ni wires or to realistic Ni(111) electrodes. It is also predicted that such atomic-scale junctions should lead to very high (ideally, infinite) magneto-resistance ratios since the electric current gets fully blocked if two electrodes have antiparallel magnetic alignment.
authors: Service de Physique de l'Etat Condensé DSM/IRAMIS/SPEC (CNRS UMR 3680), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors: Alexander
authors: A
authors: Smogunov
authors: Service de Physique de l'Etat Condensé DSM/IRAMIS/SPEC (CNRS UMR 3680), CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors: Yannick J
authors: YJ
authors: Dappe
keywords: Spin-polarized transport; atomic nanocontacts; magnetoresistance; molecular spintronics; spin-filtering