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Séminaire QUEST

Jeudi 4 février à 9h30,
Salle Rémy Lemaire, K223

Orateur : Vincent Sacksteder, Royal Holloway College, U. of London
"Toward accurate calculation of diffusive spin transport starting from realistic Hamiltonians. Applications to electrons, polaritons, holes, and Topological Insulators"

Abstract :

Spin-orbit couplings, in the presence of an electric current, can generate strong spin currents with possible applications to spintronics devices. For example, recent experiments demonstrated domain switching driven by electrical current in a CoPt bilayer with strong spin-orbit coupling. These devices depend sensitively on both their atomic-scale physics including the multilayer device profile and spin-orbit coupling, and on charge and spin flow across the whole device.
This talk will focus on a coarse-graining strategy which starts from realistic Hamiltonians describing spin and scattering at the atomic scale, and derives spin diffusion equations suitable for modeling a spintronics device. After reviewing the standard formalism, we outline how symbolic algebra can ease calculation of spin diffusion equations for Hamiltonians containing several terms, and can be extended to high orders in perturbation theory, and to strong spin-orbit coupling. We also discuss the possibility of deriving spin diffusion coefficients numerically, allowing the use of very realistic and detailed microscopic Hamiltonians. We present results for spin lifetimes, persistent spin helices, spin polarization production, and characteristic spatial patterns in TIs, hole-doped materials, polaritons, and electron gases.

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