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