Interplay of charge and heat transport in a nano-junction in the out-of-equilibrium cotunneling regime

We study the charge transport and heat transfer through a nano-junction composed of a small metallic grain weakly coupled to two metallic leads. We focus on the cotunneling regime out-of-equilibrium, where the bias voltage and the temperature gradient between the leads strongly drive electron and phonon degrees of freedom in the grain, which in turn have a strong feedback on the transport through the grain. We derive and solve the heat balance equation for electron and phonon degrees of freedom in the grain and self-consistently find the current–voltage characteristics. We demonstrate that the transport in the nano-junction is very sensitive to the spectrum of the bosonic modes in the grain. (paper)