Irreversible thermodynamics of transport across interfaces

Abstract

With spintronics applications in mind, we use irreversible thermodynamics to derive the rates of entropy production and heating near an interface when heat current, electric current, and spin current cross it. Associated with these currents are apparent discontinuities in temperature (∆T ), electrochemical potential (∆μ), and spin-dependent "magnetoelectrochemical potential" (∆μ ↑,↓ ). This work applies to magnetic semiconductors and insulators as well as metals, due to the inclusion of the chemical potential µ, which usually is neglected in works on interfacial thermodynamic transport. We also discuss the (non-obvious) distinction between entropy production and heat production. Heat current and electric current are conserved, but spin current is not, so it necessitates a somewhat different treatment. At low temperatures or for large differences in material properties, the surface heating rate dominates the bulk heating rate near the surface. We also consider the case, noted by Rashba, where bulk spin currents occur in equilibrium. Although a surface spin current (in A/m 2 ) should yield about the same rate of heating as an equal surface electric current, production of such a spin current requires a relatively large "magnetization potential" difference across the interface.Résumé : Avec applications dans l'esprit de spintronics, nous employons la thermodynamique irréversibleà obtenir les taux de production d'entropie et de chauffageà proximité d'une interface lorsque la chaleur actuelle, le courant electrique, et courant de spin la traverser. Associésà ces courants sont discontinuités apparentes de la température (∆T ), potentielélectrochimique (∆μ), et dépendant du spin potentiel "magnetoélectrochimique" (∆μ ↑,↓ ). Ce travail s'appliquè a semi-conducteurs magnétiques et isolants ainsi que des métaux, dueà l'inclusion de la potentiel chimique µ, ce qui est généralement négligée dans les travaux sur les transports thermodynamique interfaciale. Nous discutonségalement de la distinction (nonévidente) entre la production d'entropie et la production de chaleur. Chaleur actuelle et le courant electrique sont conservés, mais n'est pas courant de spin, il nécessite un traitement quelque peu différent. A basse température, ou pour de grandes différences dans les propriétés du matériau, la vitesse de chauffage de surface domine la vitesse de chauffage en vrac prés de la surface. Nous considéronségalement le cas, a noté par Rashba, oú les courants de spin en vrac se produireà l'équilibre. Même si un courant de spin de surface (en A/m 2 ) devrait donner environ le même taux de chauffage d'une surfaceégale de courantélectrique, la production d'un tel courant de spin nécessite un potentiel relativement important "aimantation différence" entre l'interface. ). details of the non-conservation of the spin current due to spinflip processes, and did not study the rate of heating near the surface. The present work considers these non-conservation phenomena, which require more refined considerations than when they are not present. (Th...

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