Thermoelectric Effects in 2D Electron Systems

We investigate the transport properties in two 2D electron systems. The first system is composed by a graphene monolayer with a Rashba coupling localized around a finite region. We calculate within the scattering approach the linear electric and thermoelectric conductance as well as the charge thermopower. We find that the junction thermopower is largely dominated by an intrinsic term independently of the spin-orbit potential scattering. We discuss the possibility of cancelling the intrinsic thermopower by resolving the Seebeck coefficient in the subband space. The second system consist on a spin-orbit-coupled two-dimensional electron system under the influence of a thermal gradient externally applied to two reservoirs. We discuss the generated voltage bias (charge Seebeck effect), spin bias (spin Seebeck effect) and magnetization-dependent thermopower (magneto-Seebeck effect) in the ballistic regime of transport. We observe that, when the contacts are ferromagnetic, the thermopower can take positive and negative values. This is very interesting since depending on the position of the Fermi energy we may tune, with a fixed difference of temperature, the direction of the electric current.