Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.44: Poster

Montag, 8. März 2004, 18:00–21:00, Bereich C

X-ray study of the surface dynamics at the charge density wave transition in NbSe2 — •Bridget Murphy1, Jochim Stettner1, Martin Müller1, Ingo Grotkopp1, Peter Boesecke2, Till H. Metzger2, Michael Krisch2, Herwig Requardt2, and Werner Press1,31Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität Kiel, Leibnizstraße 19, 24098 Kiel — 2ESRF, BP 220, 38043 Grenoble Cedex 9, France — 3Institut Laue-Langevin, BP 156, 38043 Grenoble Cedex 9, France

2H-NbSe2 is a van der Waals bonded layered structure and displays a Peierls distortion resulting in a charge density wave transition at 33K. We investigated this transition using grazing incidence X-ray diffraction and inelastic X-ray scattering. The elastically scattered intensity of the satellite reflection, which is proportional to the square of the amplitude of the modulation, as well as the respective diffuse scattering have been measured for different incidence angles in order to carry out a direct comparison between the surface and bulk behaviour. We found that the temperature dependence of the surface charge density wave satellite clearly varies from that in the bulk and that the surface transition appears to be continuous. Moreover, the surface CDW transition occurs 1.4 K above that of the bulk. We conclude that we likely observe the unusual case of a ’surface transition’. In order to improve the understanding of the dynamics phonon dispersion curves at room temperature and around the phase transition have been determined by inelastic X-ray scattering.

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