Interplay between spin heat and charge currents in strongly correlated systems

Abstract

Understanding the interplay between spin heat and charge currents is of fundamental importance in the area of Spintronics where the spin degree of freedom plays a crucial role The interaction between spin and heat currents alone is classified as the Spin Caloritronics which is basically a newly emerging sub field of Spintronics Depending on the nature of interaction among spin heat and charge degrees of freedom various kinds of thermally driven spintronic phenomena are observed and among them three distinct phenomena are now being actively investigated I The Spin Seebeck effect SSE II The anomalous Nernst effect ANE and III The magnon Hall effect MHE I The Spin Seebeck effect This pertains to the generation of pure spin current under the application of a temperature gradient 8711 T across a magnetic material A reliable way to detect this spin current is to use a normal metal NM with a large spin Hall angle e g Pt Ta or W on top of the magnetic material Thermally induced spin current is then pumped into the NM layer via the interfacial exchange interaction between itinerant and localized electrons across the interface which further gives rise to a transverse voltage via the inverse spin Hall effect ISHE II The anomalous Nernst effect This pertains to the generation of a transverse electrical voltage across a magnetic system under the application of a longitudinal thermal gradient In particular the ANE is defined in the direction orthogonal to both magnetization and the applied temperature gradient where the ANE voltage stems from the interaction between the conduction electrons with the local magnons under the influence of spin orbit interactions III The magnon Hall effect This describes the Hall effect of magnon current Even though the magnons are charged neutral they exhibit Hall transport that stems from the Berry curvature of the magnon bands Experimentally the MHE is quantified in terms of the thermal Hall effect of magnons THEM which pertains to the newline newline