Direct evidence of lattice-relaxed charge transfer exciton strings

¹ Laboratoire Léon Brillouin, CEA/CNRS - F-91191 Gif-sur-Yvette Cedex, France
² Groupe Matière Condensée et Matériaux, UMR CNRS 6626, Université Rennes 1 F-35042 Rennes Cedex, France
³ Laboratoire de Physique des Solides, Université Paris-sud F-91405 Orsay, France
⁴ Institute of Physical and Theoretical Chemistry, Technical University of Wroclaw PL-50-370 Wroclaw, Poland
⁵ Laboratoire de Cristallographie/ESRF, CNRS BP 166 F-38042 Grenoble cedex 09, France
⁶ Institute of Physics, Adam Mickiewicz University PL-61-614 Poznań, Poland
⁷ Physikalisches Institut, Universität Stuttgart D-70550 Stuttgart, Germany

Received: 2 April 2001
Accepted: 23 October 2001

Abstract

We report first direct evidence, by X-ray diffuse scattering, of lattice-relaxed charge transfer exciton strings, which are one-dimensional self-trapped multiadjacent excitons. These non-linear excitations are key objects in quasi–one-dimensional organic compounds that undergo the neutral-ionic transition and are responsible for their physical properties. The one-dimensional fluctuations are very well described within the framework of the transfer integral method and physical parameters are deduced from both X-ray and dielectric measurements.