Single molecule circuits are ideal systems for studying a wide range of quantum phenomena. The flow of an electric current across individual molecules placed between metal electrodes is determined by the junction electronic structure, which in turn is strongly affected by both the nature of the molecular backbone and the metal-molecule links. Calculations based on Density-Functional Theory and non-Equilibrium Green’s Functions can be used to understand and predict the conductance of molecular nanostructures.
I will start by discussing elastic transport focusing on the coupling between metal and molecule. I will compare the signature in conductance of different Au-molecule links and examine their behaviour under an applied bias. I will then turn to the other main ‘component’ of the circuit: the molecular backbone. Backbone properties, often with no classical equivalent, can bring important consequences for conductance.
The second part of my talk will address our recent work on the interaction of electronic and vibrational degrees of freedom. I will show how an analysis of the different contributions which make up the inelastic peaks can completely characterize the formation of the inelastic signal. I will also discuss the current-induced heating and cooling of the junction from the calculation of rates of absorption or emission of molecular vibrations by the tunneling electrons