Substrate-mediated band-dispersion of adsorbate molecular states

Charge carrier mobilities in molecular condensates are usually small, as the coherent transport, which is highly effective in conventional semiconductors, is impeded by disorder and the small intermolecular coupling. A significant band dispersion can usually only be observed in exceptional cases such as for π-stacking of aromatic molecules in organic single crystals. Here based on angular resolved photoemission, we demonstrate on the example of planar π-conjugated molecules that the hybridization with a metal substrate can substantially increase the delocalization of the molecular states in selective directions along the surface. Supported by ab initio calculations we show how this mechanism couples the individual molecules within the organic layer resulting in an enhancement of the in-plane charge carrier mobility.