Electronic transport through a light-driven azobenzene molecule switch: A revisit by density functional theory study*

Azobenzene, a molecule that changes conformation between \emph{trans} and \emph{cis} configurations, is a candidate light-driven molecule switch. Recent experiments showed that the ``on'' state with larger measured conductance is associated with the \emph{cis} isomer, which is in contrast with our previous theoretical prediction. Here we reconsider the issue of the molecule-electrode and electrode-electrode coupling by performing a first-principles study of the electronic structures and transport properties of Au-azobenzene-Au molecule junctions. Specifically, we investigate the dependence of the conductance and the current-voltage characteristics in two types of Au electrode, 2-D Au(111) surface and 1-D Au STM tip. We find that, not only the \emph{trans} to \emph{cis} transformation of the molecule, but also the electrode-electrode coupling plays a critical role in determining the conductance near the Fermi level.