Nature of the broken-symmetry phase of the one-dimensional metallic In/Si(111) surface

The phase transition of a metallic In chain structure on Si(111) was investigated by high-resolution photoemission. Core-level spectra clearly elucidate that the symmetry breaking at low temperature occurs only within the inner parts of the In chains. In the valence bands, the transition is accompanied by the formation of pseudogaps of 80–150 meV and the band backfolding with only marginal changes of the band dispersion. No sign of Luttinger liquid behavior is observed in the spectral function near the Fermi level. This result is generally consistent with the idea of a fluctuating one-dimensional charge-density wave state but conflicting with the present structure model for the low-temperature phase.