Session S2 - High-Tc Superconductors: Scattering.
INVITED session, Wednesday afternoon, March 24
517B, Palais des Congres
We give an overview of magnetic neutron scattering experiments on superconducting copper oxides, with an emphasis on a "resonant mode" that dominates the spin excitation spectrum in the superconducting states of YBCO and BSCCO compounds. Recent results include observations of the primary resonant mode in single- [1] and trilayer high-Tc materials and of a predicted secondary mode in bilayer materials [2]. We also report a detailed map of the in-plane anisotropy of the incommensurate spin dynamics in the superconducting state of untwinned, optimally doped YBCO. This map shows that the incommensurability is fully two-dimensional, that is, the peak intensity forms a ring around (\pi/a, \pi/b). However, the peak along the a-axis is narrower and about a factor of two more intense than the one along b. Finally, we report new x-ray diffraction results on oxygen vacancy ordering throughout the YBCO phase diagram. These oxygen superstructures must be taken into account when interpreting spectral anomalies in this system.
[1] H. He et al., Science 295, 1045 (2002) [2] S. Pailhes et al., cond-mat/0308394 (PRL, in press)