Symmetry-Derived Half-Metallicity in Atomic and Molecular Junctions

Alexander Smogunov 1, 2, * Yannick J. Dappe 2
* Corresponding author
1 GMT - Groupe Modélisation et Théorie
IRAMIS - Institut Rayonnement Matière de Saclay, SPEC - UMR3680 - Service de physique de l'état condensé
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.
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Alexander Smogunov, Yannick J. Dappe. Symmetry-Derived Half-Metallicity in Atomic and Molecular Junctions. Nano Letters, American Chemical Society, 2015, 15 (5), ⟨10.1021/acs.nanolett.5b01004⟩. ⟨cea-01366488⟩

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