Image-charge induced localization of molecular orbitals at metal-molecule interfaces: Self-consistent GW calculations

摘要

Quasiparticle (QP) wave functions, also known as Dyson orbitals, extend theconcept of single-particle states to interacting electron systems. Here weemploy many-body perturbation theory in the GW approximation to calculate theQP wave functions for a semi-empirical model describing a $\pi$-conjugatedmolecular wire in contact with a metal surface. We find that image chargeeffects pull the frontier molecular orbitals toward the metal surface whileorbitals with higher or lower energy are pushed away. This affects both thesize of the energetic image charge shifts and the coupling of the individualorbitals to the metal substrate. Full diagonalization of the QP equation and,to some extent, self-consistency in the GW self-energy, is important todescribe the effect which is not captured by standard density functional theoryor Hartree-Fock. These results should be important for the understanding andtheoretical modeling of electron transport across metal-molecule interfaces.