Temperature and momentum dependence of the spectral function of the charge-density wave and of the normal α phase of Pb/Ge(111)

Angle-resolved high-resolution photoemission spectra of the α phase of Pb/Ge(111)-(√3×√3)R30° have been measured below (100 K) and above (300 and 500 K) the transition to a charge-density-wave insulator state. The spectra strongly differ from those expected from the published local density approximation calculations showing a surface band without dispersion and correlation and fluctuation effects also at high temperature. A pseudogap is observed at 100 K.