Europhys. Lett.
Volume 66, Number 2, April 2004
Page(s) 246 - 252
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 April 2004
Europhys. Lett., 66 (2) , pp. 246-252 (2004)
DOI: 10.1209/epl/i2003-10182-3

Low-frequency structural dynamics in the incommensurate composite crystal $\chem{Bi_2Sr_2CuO}$ ${_{6+\delta}}$

J. 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 $\chem{Bi_2Sr_2CuO}$ ${_{6+\delta}}$ ( $\chem{Bi}$-2201) system. As in the $\chem{Bi}$-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