First-principles many-body calculations of electronic conduction in thiol- and amine-linked molecules
The electronic conductance of a benzene molecule connected to gold electrodes via thiol, thiolate, and amino anchoring groups is calculated using nonequilibrium Green functions in combination with the fully selfconsistent GW approximation. The calculated conductance of benzenedithiol and benzenediamine is five times lower than predicted by standard density functional theory (DFT) in very good agreement with experiments. In contrast, the widely studied benzenedithiolate structure is found to have a significantly higher conductance due to the unsaturated sulfur bonds. These findings suggest that more complex gold/thiolate structures where the thiolate anchors are chemically passivated by Au adatoms are responsible for the measured conductance. Analysis of the energy level alignment obtained with DFT, Hartree-Fock and GW reveals the importance of self-interaction corrections (exchange) on the molecule and dynamical screening at the metal-molecule interface. The main effect of the GW self-energy is to renormalize the level positions, however, its influence on the shape of molecular resonances also affects the conductance. Non-selfconsistent G0W0 calculations, starting from either DFT or Hartree-Fock, yield conductance values within 50% of the selfconsistent GW results.