Spin and charge caloritronics in bilayer graphene flakes with magnetic contacts

TL;DR

This paper explores how magnetic configurations in bilayer graphene nanostructures influence spin and charge thermoelectric effects, revealing conditions that optimize energy conversion efficiency and spin current utilization.

Contribution

It demonstrates the impact of magnetic alignment on thermoelectric properties and introduces the potential of graphene nanosystems for energy harvesting using spin currents.

Findings

Charge Seebeck effect is enhanced in antiparallel magnetic configuration.

Parallel magnetic alignment optimizes the figure of merit ZT.

Spin ZT can double the charge ZT above 300 K.

Abstract

We investigate the coupling of spin and thermal currents as a means to rise the thermoelectric efficiency of nanoscale graphene devices. We consider nanostructures composed of overlapping graphene nanoribbons with ferromagnetic contacts in different magnetic configurations. Our results show that the charge Seebeck effect is greatly enhanced when the magnetic leads are in an antiparallel configuration, due to the enlargement of the transport gap. However, for the optimization of the charge figure of merit ZT it is better to choose a parallel alignment of the magnetization in the leads, because the electron-hole symmetry is broken in this magnetic configuration. We also obtain the spin-dependent Seebeck coefficient and spin figure of merit. In fact, the spin ZT can double its value with respect to the charge ZT for a wide temperature range, above 300 K. These findings suggest the potential value of graphene nanosystems as energy harvesting devices employing spin currents.