Tunable transport by controlling the structure of a STM molecular junction: synchronizing theory and experiments.

Prof. Dr. Gianaurelio Cuniberti, Dresden University of Technology [Homepage]

Prof. Dr. Michael Rohlfing, University of Osnabrück [Homepage]

Prof. Dr. Stefan Tautz, Forschungszentrum Jülich [Homepage]

In an ideal experiment on quantum transport through a single molecule, the structure of the
molecular wire junction – including contact geometry and molecular conformation – is under
control at the atomic level and can be measured in parallel to the transport characteristics of the
molecular wire junction. Such an experiment would offer fascinating opportunities for the
theoretical simulation and understanding of the transport at the ab intio level, because theorists
would know exactly which geometry and electronic contact properties generate the observed
transport behaviour.
In the present collaborative proposal between one experimental and two theoretical groups we
aim to move towards the ideal described above, by focussing on molecular transport experiments
carried out with an STM tip which is moved into chemical contact with a structurally and
electronically well‐characterized molecular adsorbate on a single‐crystalline metal surface. The
excellent imaging and manipulation properties of the STM allow contacting the molecule at welldefined
functional groups and modifying the molecule‐substrate contact controllably by tip
manipulation. With this approach we aim for a benchmark study of electronic transport in
molecular wires, synchronizing experiment and theory (electronic structure and transport) from
the very outset by treating geometric junction structure, electronic junction properties and
transport behaviour comprehensively and on an equal footing. We will focus on carefully selected
model wires for which the viability of the present approach has already been demonstrated,
experimentally and theoretically. The project will thus provide the basis for the design of tailored
molecular junctions and molecular switches, both of them important elements of single‐molecule
electronics.