Two distinct metallic bands associated with monatomic Au wires on the Si(557)-Au surface

The Si(557)-Au surface, containing monatomic Au wires parallel to the steps, has been proposed as an experimental realization of an ideal one-dimensional metal. In fact, recent photoemission experiments on this system (Nature 402, 504 (1999)) found two peaks that were interpreted in terms of the spin-charge separation in a Luttinger liquid. Our first-principles density functional calculations reveal two metallic bands associated with Au-Si bonds, instead of the single band expected from the Au 6s states, providing an alternative explanation for the experimental observations.