Seminars Archive

The electronic structure of (Pb)Sn/Ge(111) in the (sqrt 3 x sqrt 3)R30? alfa-phase and (3x3) CDW phase

Abstract
The alfa-phase of Pb/Ge(111) and the isostructural Sn/Ge(111) (sqrt 3 x sqrt 3)R30? phase show a transition to a commensurate charge density wave (CDW) structure at low temperature. Angle resolved photoemission spectra of 0.3 ML of Sn on Ge(111) show a transition from a delocalized Sn induced surface state at 295 K in the metallic (sqrt 3xsqrt 3) phase to a localized state with negligible momentum dispersion in the (3x3) CDW phase at 110 K. The opening of a pseudo gap at the Fermi level in the CDW phase is observed in photoemission and electron energy loss spectra. These effects and the value of the Fermi momentum in the TK direction measured by photoemission indicate that the transition to the surface charge density wave phase is caused by correlation effects and not by the nesting of the Fermi surface.