Oxygen mobility in YBa₂Cu₃O_7-δ: A Raman study

From Raman measurements on superconducting and non-superconducting YBa2Cu3O7-δ single crystals, we show that close to room temperature there is an unaccounted for, intense, oxygen vibrational mode at 598 cm-1. This (zz) polarized mode appears to arise from some chain oxygen atoms occupying another site in the crystal. Using laser heating and a shutter, we find that the time it takes to occupy or empty this site is less than 0.1 sec. If a charge carrier in the Cu-O plane induces the occupation of this new site, then a large electron-phonon coupling constant could result. © 1990.