We investigated various areas of impurity-free YBa2Cu3O7-δ single crystals with Raman spectroscopy. A definite correlation between the appearance of the group- theoretically forbidden chain-related Raman lines at 232 and 598 cm-1 and the superconductivity-induced self-energy effects observed for the 340 cm-1 B1g-like mode was established: Disorder in the chains in pure crystals has a similar effect as the introduction of impurity atoms, both leading to an increased gap value for 2Δ/kTc as deduced from the phonon self-energy effects. The absence of the forbidden chain modes in the Raman spectra may be used as an extremely sensitive quality criterion of impurity-free crystals.
ASJC Scopus subject areas
- 化学 (全般)