Spin-valley coupled caloritronics with strained honeycomb lattices

Abstract

The miniaturization of circuit components introduces the problem of localized heating that can give rise to temperature overshoots and degradation in circuit reliability. While the generated heat can be removed, a profitable spin-off is to transform the heat current into electric power taking advantage of the Seebeck effect. This constitutes the basis for electric-thermal energy conversion. The optimization of Seebeck-based power conversion techniques [1], of late, have received much attention as newer materials, notably graphene, hold promise of better thermoelectric operation demonstrated by a higher thermoelectric figure of merit, $ZT$, However, the absence of a finite band gap in graphene largely precludes its applicability; this shortcoming is alleviated in other two-dimensional (2D) gapped honeycomb lattices. The laboratory-grown silicene, germanene, and stanene (identified as the X-enes) with a buckled structure and gapped Dirac cones offer a viable alternative. Here, combining first-principles and analytic calculations, we examine a strained ferromagnetic X-ene based caloritronic device wherein a spin and valley resolved current $(I_{\\mathrm{t}\\mathrm{h}})$ flows on account of a temperature $(T)$ gradient created difference in Fermi distribution $(f)$ at the contacts.