2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session H38: Focus Session: Theory of Electron Transport Through Molecules I
8:00 AM–10:48 AM,
Tuesday, March 17, 2009
Room: 410
Sponsoring
Unit:
DCP
Chair: Matthias Ernzerhof, Université de Montréal
Abstract ID: BAPS.2009.MAR.H38.1
Abstract: H38.00001 : The Role of Symmetry in Molecular Electronic Conduction
8:00 AM–8:36 AM
Preview Abstract
Abstract
Author:
Jeffrey Reimers
(University of Sydney, Australia)
The Greens Function Density-Functional Tight-Binding (gDFTB)
method is
applied to determine the role that molecular symmetry in
single-molecule
conductivity.~ Both coherent elastic electron transport and
inelastic
electron-tunnelling spectroscopy (IETS) are considered.~ Symmetry
becomes
manifest in various ways: through the molecular point-group
symmetry of the
conducting molecule (D$_{2h}$ for chemisorbed benzenedithiol
between two
gold electrodes), through the conductance point-group symmetry
displayed by
the gDFTB equations (this embodies junction asymmetry and may be
very low
and nominally non-existent), and through an approximate
molecular-conductance point group (C$_{2v}$ for chemisorbed
benzenedithiol).~ Indeed, the conductivities for a range of relevant
problems are well approximated using the restriction of
molecular-conductance point-group.~ This allows the complex
transmission
curves calculated by many research groups to be dramatically
simplified and
partitioned into symmetry-depicted channels.~ Means are
introduced that
isolate a very small number of component channels describing
different
aspects of single-molecule conductivity: input junction channels,
through-molecule channels, and output-junction channels. For elastic
transport, all through-molecule channels are totally symmetric
and hence a
rigorous selection rule appears that transport is allowed
involving only
input-junction and output-junction channels of the same
symmetry.~ However,
for IETS, the through-molecule channels have the symmetry of the
scattering
molecular vibration and hence the input-junction and
output-junction channel
symmetries may vary.~ In general, just one channel is expected to
dominate
the junctions, leading to the IETS propensity rule that totally
symmetric
transitions are the most intense ones. Simple physical pictures are
presented showing the input, vibrational scattering, and output
channels for
IETS, leading to predictions of how this effect can be controlled
chemically.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.H38.1