Mechanisms of vibrational assisted electronic transport through single paraphenyl molecules
investigated by electron and light spectroscopy

Prof. Dr. Jose I. Pascual, Freie Universität Berlin [Homepage]

Charge transport through a single molecule excites molecular vibrations, and the coupling of
them with electronic molecular states conform the transmission channels of an electron through the
nanodevice. In this project we aim to resolve the effect of an intramolecular vibration on the
transport of charge by characterizing its transmission fingerprint and the light emitted. We focus
our research on a family of para-phenylene molecules, linear polymers in which the torsion of a
phenyl ring connects two electronic states with different transport properties. Using a scanning
tunnelling microscope at low temperature we will form stable single molecule junctions by
controlled manipulation of adsorbed molecules on a surface and apply our spectroscopy expertise
(electronic and vibrational) to identify the transport mechanism and to quantify the role of torsional
modes. Various molecular lengths and chemical end groups will allow us to tune transport
properties. The molecular temperature and the light emitted will be investigated to complement a
conceptual picture of phonon assisted transport. In particular, we aim to characterize radiative
processes like luminescence or thermal emission because they can provide useful information on
intramolecular energy redistribution and dynamical process occurring during the transport of
charge through one molecule.