Single-molecule-mediated heat current between an electronic and a bosonic bath

Abstract

In molecular devices, electronic degrees of freedom are coupled to vibrational modes of the molecule, offering an opportunity to study fundamental aspects of this coupling at the nanoscale. To this end, we consider the nonequilibrium heat exchange between a conduction band and a bosonic bath mediated by a single molecule. For molecules large enough so that onsite Coulomb repulsion can be dropped, we carry out an asymptotically exact calculation of the heat current, governed by the smallness of the electron-phonon coupling, and obtain the steady-state heat current driven by a finite-temperature drop. At low temperatures, the heat current is found to have a power-law behavior with respect to the temperature difference with the power depending on the nature of the bosonic bath. At high temperatures, on the other hand, the current is linear in the temperature difference for all types of bosonic baths. The crossover between these behaviors is described. Some of the results are given a physical explanation by comparing to a perturbative master-equation calculation (the limitation of which we examine). © 2014 American Physical Society.