Molecular quantum well at the C₆₀∕Au(111) interface

A molecular quantum well is observed in epitaxial thin films of C₆₀ on Au(111). This quantum well is characterized by nearly free-electron-like dispersion in the surface plane and splitting of the electronic band with increasing number of C₆₀ overlayers. The experimental quantum well structure can be well described by tight binding theory with an intermolecular charge transfer integral of β=−33±3 meV, corresponding to a full bandwidth of 400±40 meV. Quantum mechanical calculation based on time-dependent density functional theory provides excellent agreement with this β value. The molecular quantum well is populated by photoinduced electron transfer from the Au substrate and has a transient lifetime of 4 fs<t<20 fs.