Inelastic neutron scattering in cuprate superconductors: Evidence for inhomogeneous materials properties

Abstract

There is increasing experimental evidence for the coexistence of different types of local regions in doped high-Tc superconductors of “123” and “214” type. They may be classified into local regions of undoped, intermediately doped, and highly doped character. The doping mechanism makes the system inhomogeneous, and the superconducting state is reached by a percolation process. Very detailed information about the volume fractions and the spatial extent of the local regions can be obtained by neutron spectroscopic investigations of the crystal-field interaction at the rare-earth site which is an ideal local probe of the charge distribution in the superconducting copper oxide planes. The inhomogeneous materials properties have to be taken into account in any interpretation of the physical properties of doped high-Tc superconductors. This is exemplified for the static and dynamic copper spin correlations of YBa2Cu3Ox (6≤x≤7). We show that the spin fluctuations observed in the superconducting state can be associated with the undoped and intermediately doped regions of the system, whereas no magnetic scattering occurs for the highly doped regions.