Interference and Molecular TransportA Dynamical View: Time-Dependent Analysis of Disubstituted Benzenes

The primary issue in molecular electronics is measuring and understanding
how electrons travel through a single molecule strung between two
electrodes. A key area involves electronic interference that occurs
when electrons can follow more than one pathway through the molecular
entity. When the phases developed along parallel pathways are inequivalent,
interference effects can substantially reduce overall conductance.
This fundamentally interesting issue can be understood using classical
rules of physical organic chemistry, and the subject has been examined
broadly. However, there has been little dynamical study of such interference effects. Here, we use the simplest electronic
structure model to examine the coherent time-dependent transport through
meta- and para-linked benzene circuits, and the effects of decoherence.
We find that the phase-caused coherence/decoherence behavior is established
very quickly (femtoseconds), that the localized dephasing at any site
reduces the destructive interference of the meta-linked species (raising
the conductance), and that thermal effects are essentially ineffectual
for removing coherence effects.