Organic Quantum dot arrays: Tunable energy and mass renormalization by homothetic porous networks

Abstract

Organic nanoporous networks grown on (111) noble metal surfaces, also referred to as quantum dot arrays since they can confine surface state electrons, are highly successful model systems to study scattering phenomena. On such surfaces, the 2D molecular scaffolds, commonly exhibit an upward energy shift of the Shockley state and the formation of shallow bands, which results from the repulsive scattering at the molecular walls and partial quantum confinement within each nanodot. In this work, we present experimental evidence of a tunable downward energy shift through scalable metalorganic nanoporous networks grown on Au(111). The electronic structure is determined by two state-ofthe- art, highly complementary techniques (STM and ARPES), and supported by first principles and model calculation. Notably, the counterintuitive downshift is gradual with decreasing pore size and increasing adatom density, something that cannot be explained through standard quantum confinement in the molecular cavity. Therefore we assign the origin of this effect to metal-organic overlayer-substrate interactions in the form of adatom-surface state hybridizations. This local coupling keeps the Shockley state nature, but renormalizes it, thereby changing its fundamental energy and effective mass. The absence to date of the experimental band structure resulting from single adatom metal-coordinated nanoporous networks has precluded the observation of the significant surface state renormalization we have observed.