AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP5
Correlation Effects and Origin of the Phase Transition in Pb/Ge(111)

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: A. Mascaraque, Universidad Autonoma Madrid, Spain
Authors: A. Mascaraque, Universidad Autonoma Madrid, Spain
J. Avila, LURE and CSIC, France
M.C. Asensio, LURE and CSIC, France
E.G. Michel, Universidad Autonoma Madrid, Spain
Correspondent: Click to Email
The @sr@3 x @sr@3-Pb/Ge(111) structure undergoes a phase transition to a @sr@3 x @sr@3 phase at low temperature (LT),@footnote 1@ which has been interpreted as the stabilization of a charge-density-wave.@footnote 1@ The role of correlation effects and Fermi surface (FS) nesting as driving forces of the transition has been considered.@footnote 1,2@ We report an investigation on the electronic structure and Fermi surface of Pb/Ge(111) along the phase transition using angle-resolved photoemission. Pb/Ge(111) exhibits a prominent Pb p@sub z@ dispersing surface state at RT, that splits in two dispersing bands at LT. We monitored in detail the intensity at the Fermi energy, both at room temperature (RT) and LT, in different points of the surface Brillouin zone. While there is an overall intensity decrease at LT, the effect is more pronounced at 1/2@GAMMA@K, suggesting that the LT phase is indeed metallic. The role of correlation effects and FS nesting was also tested by measuring the dispersion of the surface features both at LT and RT. The evidences found support that nesting is not the driving force of the transition. However, the modifications observed in the LT electronic structure indicate a significant gain in electronic energy along the phase transition. These findings will be discussed in view of existing theoretical models. @FootnoteText@ @footnote 1@J.M. Carpinelli et al., Nature 381, 398 (1996). @footnote 2@A. Goldoni et al, Phys.Rev. B 55, 4109 (1997).