Incommensurate composite structure of the superconductor Bi2Sr2CaCu2O8+δ

We have performed elastic neutron scattering experiments, using a high-quality single crystal of the high-T-c superconductor Bi2Sr2CaCu2O8+delta a By a systematic comparison of intensities between superlattice reflections, we show that the one-dimensional incommensurate modulated model, usually used to interpret the structural characteristics, exhibits important failures. In contrast, in accordance with theoretical predictions [M. B. Walker and W. Que, Phys. Rev. B 45, 8085 (1992)], a composite structure made of two interpenetrating subsystems can alternatively describe the incommensurate structure and account for the hierarchy of the observed intensities.