  In this paper we investigate the effect of strong electronic interactions on
the thermoelectric properties of a simple generic system, consisting of a
single correlated layer sandwiched between two metallic leads. Results will be
given for the linear response regime as well as beyond, for which a full
nonequilibrium many-body calculation is performed, based on nonequilibrium
dynamical mean-field theory (DMFT). As impurity solver we use the auxiliary
master equation approach, which addresses the impurity problem within a finite
auxiliary system consisting of a correlated impurity, a small number of
uncorrelated bath sites and Markovian environments. For the linear response
regime, results will be presented for the Seebeck coefficient, the electrical
conductance and the electronic contribution to the thermal conductance. Beyond
linear response, i.e. for finite differences in the temperatures and/or the
bias voltages in the leads, we study the dependence of the current on various
model parameters, such as gate voltage and Hubbard interaction of the central
layer. We will give a detailed parameter study as far as the thermoelectric
efficiency is concerned. We find that strong correlations can indeed increase
the thermopower of the device. In addition, some general theoretical
requirements for an efficient thermoelectric device will be given.
