Incommensurate Quantum Size Oscillations of Oligoacene Wires Adsorbed on Au(111)

Acenes have attracted interest for a long time partly because of their electronic structure and partly because they are expected to show interesting correlation effects. For the isolated molecules, our recent theoretical work suggests a possibility for oscillations of the excitation gaps with the length of the molecule. In view of the recent experimental progress of on-surface synthesis, we employ the density functional theory to investigate here the fate of these oscillations for oligoacenes adsorbed on a Au(111) surface. We show that the surface perturbs the oligoacene gaps seen in isolation only weakly, implying that incommensurate oscillations survive. Effects beyond the density functional description (correlations, charging effects) are discussed.