Abstract
We report results of far-infrared spectroscopic measurements on a series of isotopically O) exchanged and isomorphically substituted materials in the and families. Based upon these measurements, we propose assignments for phonons in both the semiconducting phase and the superconducting phase. In , the lowest-frequency phonon at 155 is seen to shift ∼2% to lower frequency when compared to the material, demonstrating the role of oxygen in this vibration (which we have previously assigned as a c-axis-directed Cu-O chain bending mode of symmetry). This transverse-optical branch may be important for phonon-mediated superconductivity in this material, as indicated in a recent theoretical treatment by Weber and Matthiess [Phys. Rev. B 37, 599 (1988)].
- Received 8 August 1988
DOI:https://doi.org/10.1103/PhysRevB.38.11382
©1988 American Physical Society