Thermoelectric transport parallel to the planes in a multilayered Mott-Hubbard heterostructure

Abstract

We present a theory for charge and heat transport parallel to the interfaces of a multilayer (ML) in which the interfacing gives rise the redistribution of the electronic charges. The ensuing electrical field couples self-consistently to the itinerant electrons, so that the properties of the ML crucially depend on an interplay between the on-site Coulomb forces and the long range electrostatic forces. The ML is described by the Falicov-Kimball model and the self-consistent solution is obtained by iterating simultaneously the DMFT and the Poisson equations. This yields the reconstructed charge profile, the electrical potential, the planar density of states, the transport function, and the transport coefficients of the device. We find that a heterostructure built of two Mott-Hubbard insulators exhibits, in a large temperature interval, a linear conductivity and a large temperature-independent thermopower. The charge and energy currents are confined to the central part of the ML. Our results indicate that correlated multilayers have the potential for applications; by tuning the band shift and the Coulomb correlation on the central planes, we can bring the chemical potential in the immediate proximity of the Mott-Hubbard gap edge and optimize the transport properties of the device. In such a heterostructure, a small gate voltage can easily induce a MI transition. This switching does not involve the diffusion of electrons over macroscopic distances and it is much faster than in ordinary semiconductors. Furthermore, the right combination of strongly correlated materials with small ZT can produce, theoretically at least, a heterostructure with a large ZT.