Zero-field mu SR study of YBa2Cu3O6+x, x >= 0.67: evidence for charge ordering

摘要

Zero-field (ZF) muSR measurements were performed on single crystals of the high temperature superconductor YBa2Cu3O6+x for x greater than or equal to 0.67. Contrary to early ZF-muSR studies, we find that the muon-spin relaxation function evolves significantly as a function of temperature and oxygen content. The relaxation rate of the ZF-muSR time spectra exhibits a local minimum near 55 K and a subsequent increase with decreasing temperature. These features weaken considerably with decreasing x. A comparison to the results of nuclear quadrupole resonance experiments on highly doped samples suggests that these observations are associated with the build up of long-range charge correlations and not spontaneous orbital moments as suggested by Sonier et al. (Science 292 (2001) 1692). (C) 2002 Elsevier Science B.V. All rights reserved. [References: 8]