Scanning Tunneling Microscopy Observation of an Electronic Superlattice at the Surface of Clean Gold

We have used scanning tunneling spectroscopy to spatially resolve the electronic structure of clean Au(111) at low temperature. We find that the long-range herringbone reconstruction on Au(111) acts as a superlattice for surface-state electrons, creating a new band structure and modulated electronic density. Low energy electrons respond to the superlattice by localizing in the hexagonal-close-packed (hcp) region of the reconstruction, while higher energy electrons reverse this trend, shifting density back to the adjacent face-centered-cubic (fcc) region. These observations are quantitatively explained by an extended Kronig-Penney model, from which we estimate the well-depth of the reconstruction-induced surface superlattice.