Electronic structure change in order–disorder phase transition on surface

Recent studies have shown that the Si ( 1 1 1 ) 3 × 3 – Ag surface system undergoes a phase transition, accompanying changes in its electronic structure including band splitting as observed by photoemission spectroscopy. We study this system through Monte Carlo simulation considering the disordered nature of the system at high temperature. We construct a simple model for generating the surface atom arrangements and calculate the surface electronic states using a tight-binding model. As the reciprocal space vector is not a good quantum number for the obtained electronic states in the disordered phase, we make a projection of the density of state into the reciprocal space (RDOS) to compare experimental photoemission spectra. Despite of the absence of long-range ordering, the short-range ordering causes the characteristic features of energy dispersion before and after the phase transition as indicated in the calculated RDOS.