Thermoelectric Signatures of Coherent Transport in Single-Molecule Heterojunctions

An exact expression for the heat current in an interacting nanostructure is derived and used to calculate the thermoelectric response of three representative single-molecule junctions formed from isoprene, 1,3-benzenedithiol, and [18]-annulene. Dramatic enhancements of the thermopower S and Lorenz number L are predicted when the junction is tuned across a node in the transmission function, with universal maximum values Smax = (π/31/2)(kB/e) and Lmax = (7π2/5)(kB2/e2). The effect of a finite minimum transmission probability due, e.g., to incoherent processes or additional nonresonant channels, is also considered.