Geometry of the valence transition induced surface reconstruction of Sm(0001)

E. Lundgren1, J. N. Andersen1, R. Nyholm1, X. Torelles2, J. Rius2, A. Delin3, A. Grechnev3, O. Eriksson3, C. Konvicka4, M. Schmid4, P. Varga4

1 Department of Synchrotron Radiation Research, Institute of Physics, Lund University, S-22100 Lund, Sweden
2 Institut de Ciencia de Materials de Barcelona (C.S.I.C), 08193, Bellaterra, Barcelona, Spain
3 Department of Physics, Uppsala University, Box 530 Uppsala, Sweden
4 Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria

Phys. Rev. Lett. 88 (2002) 136102

We present a structural determination of the surface reconstruction of the Sm(0001) surface using surface x-ray diffraction, scanning tunneling microscopy and ab-initio calculations. The reconstruction is associated with a very large (22 %) expansion of the atomic radius for the top monolayer surface Sm atoms. The mechanism driving the surface reconstruction in Sm is unique among all elements and is closely connected to the strong correlations of the 4f electrons in Sm and the intermediate valence observed in certain Sm compounds. The atoms constituting the top monolayer of Sm(0001) have vastly different chemical properties compared to the layer underneath and behave as if they were an adsorbate of a different chemical species.

Corresponding author: E. Lundgren. Reprints also available from M. Schmid (schmid< encoded email address >).

Users with online access to Phys. Rev. Lett. can load the article from the publisher.