Low-frequency structural dynamics in the incommensurate composite crystalJ. Etrillard1, 2, L. Bourgeois1, P. Bourges1, B. Liang3, C. T. Lin3 and B. Keimer3
1 Laboratoire Léon Brillouin, CEA-CNRS, CE Saclay - 91191 Gif-sur-Yvette, France
2 Groupe Matière Condensée et Matériaux, UMR au CNRS 6626 Université de Rennes I - 35042 Rennes Cedex, France
3 Max-Planck-Institut für Festkörperforschung - 70569 Stuttgart, Germany
(Received 15 October 2003; accepted in final form 6 February 2004)
Inelastic coherent neutron scattering experiments have been performed to study the low-frequency structural excitations in single crystals of the incommensurate superconducting ( -2201) system. As in the -2212 family, the observation of two well-defined propagating "acoustic-like" branches around the main Bragg reflections reflects its composite nature. The two modes naturally correspond to the separate motions of the two sublattices. Constant- Q scans reveal a rapid evolution of the dynamical structure factor with the wave vector.
61.44.Fw - Incommensurate crystals.
63.20.Dj - Phonon states and bands, normal modes, and phonon dispersion.
61.12.-q - Neutron diffraction and scattering.
© EDP Sciences 2004