Thermoelectric and inelastic effects in charge transport through atomic and molecular contacts

The interaction of electrons and phonons leads to ordinary phenomena such as the heating of electric circuits upon current flow. For the miniaturization of electronic devices, the removal of heat plays an increasingly important role. Beside the typically unwanted dissipative effects, inelastic processes also provide crucial physical information that is ignored in the frequently used theoretical descriptions treating transport through nanosystems as an elastic, energy-conserving process.

Through combined experimental and theoretical studies of different transport properties, this project will improve the understanding of the influence of electron-vibration coupling on the charge transport. Nanostructures that can be understood as components of complex devices will allow comparing atomistic models without system-dependent parameters and the experiment. Specifically, molecular contacts shall be studied in detail using inelastic electron tunneling spectroscopy as well as the signatures of excited vibrations in the shot noise. In addition, thermoelectric nonequilibrium effects shall be explored.

Chain of gold atoms connected to gold electrodes

Fig.1: (a) Chain of four gold atoms connected to gold electrodes. All atoms in the region “C” have been relaxed. The dynamic regions, where atoms can vibrate, are marked as DR1 and DR2. (b) Energy-dependent transmission τ(E) and the four highest transmission probabilities τ1(E) to τ4(E) of the eigenchannels. (c) Wave-functions Ψ1 to Ψ4 of the corresponding, left-incoming transmission eigenchannels, evaluated at the Fermi energy.