# Spin-valley coupled thermoelectric energy converter with strained honeycomb lattices

## TL;DR

This paper proposes a thermoelectric energy converter using strained honeycomb lattices like silicene, exploiting spin-valley locking and external modulation to optimize charge, spin, and valley currents for improved efficiency.

## Contribution

It introduces a novel caloritronic device leveraging spin-valley coupling in 2D materials, with quantitative analysis and optimization strategies for thermoelectric performance.

## Key findings

- Finite charge, spin, and valley currents are generated under temperature gradients.
- Uniaxial strain and electric fields modulate these currents effectively.
- Expressions for thermoelectric efficiency and figure of merit are derived and optimized.

## Abstract

A caloritronic device setup is proposed that harnesses the intrinsic spin-valley locking of two-dimensional honeycomb lattices with graphene-like valleys, for instance, silicene and stanene. Combining first-principles and analytic calculations, we quantitatively show that when sheets of such materials are placed on a ferromagnetic substrate and held between two contacts at different temperatures, an interplay between the electron degrees-of-freedom of charge, spin, and valley arises. A manifestation of this interplay are finite charge, spin, and valley currents. Uniaxial strain that adjusts the buckling height in silicene-type of lattices, in conjunction with an applied electric field, is shown to further modulate the aforementioned currents. We link these calculations to a Seebeck-like thermopower generator and obtain expressions (and means to optimize them) for two spin-valley polarized performance metrics--the thermodynamic efficiency and thermoelectric figure of merit. A closing summary outlines possible enhancements to presented results through the inherent topological order and substrate-induced external Rashba spin-orbit coupling that exists in silicene-type materials.