Cooperative structural and Peierls transition of indium chains on Si(111)

We have performed high-resolution angle-resolved photoemission spectroscopy on quasi-one-dimensional indium chains on the Si(111) surface to study the temperature-induced metal-insulator (MI) transition accompanied by the 4×1 to 8×2 structural change. The band dispersion near EF shows an abrupt change at 120 K, giving a relatively large energy gap compared to the energy scale of the transition temperature. The band dispersion of the 8×2 phase shows no discernible temperature evolution, in sharp contrast to the conventional simple Peierls or structural transition. The experimental results suggest that the Peierls instability is important in the MI transition, while other structural effects are cooperatively involved.