Spin-caloritronic transport in hexagonal graphene nanoflakes
arXiv:2003.01139 · doi:10.1103/PhysRevB.102.035160
Abstract
We investigate the spin-dependent thermoelectric effect of graphene flakes with magnetic edges in the ballistic regime. Employing static, respectively, dynamic mean-field theory we first show that magnetism appears at the zigzag edges for a window of Coulomb interactions that increases significantly with increasing flake size. We then use the Landauer formalism in the framework of the non-equilibrium Green's function method to calculate the spin and charge currents in magnetic hexagonal graphene flakes by varying the temperature of the junction for different flake sizes. While in non-magnetic gated graphene the temperature gradient drives a charge current, we observe a significant spin current for hexagonal graphene flakes with magnetic zigzag edges. Specifically, we show that in the "meta" configuration of a hexagonal flake subject to weak Coulomb interactions, a pure spin current can be driven just by a temperature gradient in a temperature range that is promising for device applications. Bigger flakes are found to yield a bigger window of Coulomb interactions where such spin currents are induced by the magnetic zigzag edges, and larger values of the current.
arXiv comment12 pages, 7 figures; published version with expanded discussion of edge magnetism (section III A) and some other smaller changes
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