Quantum fluctuation and dissipation effects
in vibration-assisted single-molecule transport

Prof. Dr. Herbert Schoeller, RWTH-Aachen [Homepage]

Prof. Dr. Maarten R. Wegewijs, Forschungszentrum Jülich [Homepage]

Fundamental questions regarding charge and energy transport in a single molecule
transistor are closely related to the mechanical degrees of freedom. Experimentally
one finds suppression of single-electron transport due to both Franck-Condon
effects related to the molecular vibrations and due to Coulomb charging. As a
result, two-electron tunneling processes carry a significant part of the current. In
the First Period of the SPP we have developed for the first time a consistent realtime
transport theory to calculate these processes for a general model, and have
applied it to basic models for vibrational effects in molecules. In the Second Period
we will also systematically treat the effects of dissipative environments with
the same accuracy, i.e. accounting for 2nd order energy transport processes, as
well as novel quantum coherent energy-charge transport processes. This allow us
to analyze the interplay between mechanical and electronic quantum fluctuations
and dissipation, a topic central to molecular device operation at low temperature.
Furthermore, we will pioneer the open problem of environment assisted
tunneling in 2nd order in the tunneling. This provides an effective method for
treating many molecular vibrations , while accounting for higher order charge and
energy transport processes and strong interactions. We will apply the method to
the Anderson-Holstein model and to molecular models with multiple vibrations,
where interesting effects of electron-vibration entanglement are expected due to
pseudo Jahn-Teller interactions.