Evidence for Large Static and Dynamic Distortions in High tc Superconducting YBa2Cu3O7-δ Crystals over a Wide Temperature Range

Large deviations from the expected atomic thermal vibrational amplitude in Cu-O rows in a YBa2Cu3O7-δ (Tc=92.5 K) crystal have been observed in a wide temperature range (300 endash 30K) by ion channeling. In contrast, Y-Ba as well as Cu-O rows in nonsuperconducting deoxygenated YBa2Cu3O6.2 specimens show a normal decrease in the atomic vibrational amplitude as the sample temperature is lowered. These anomalous results in the YBCO superconductor provide a clear indication of uncorrelated static and dynamic distortions associated with Cu-O rows. Possible implications of these structural changes are discussed. copyright 1996 The American Physical Society