Incommensurate composite structure of the superconductor Bi2Sr2CaCu2O8+delta

We have performed elastic neutron scattering experiments, using a high-qual ity 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 int erpenetrating subsystems can alternatively describe the incommensurate stru cture and account for the hierarchy of the observed intensities.