Abstract
The axial oxygen contributions to the Cu K-edge, polarized, extended x-ray-absorption fine structure of are analyzed from 10≤T≤105 K, using a novel approach in which the radial distribution function is directly calculated from model potentials. The best fit is obtained with a double-well potential with two nearly equally populated O(4) sites 0.13 Å apart. The site separation decreases 0.02 Å in a region near . This perturbation in the structure is accompanied by a large increase of the tunneling frequency of ∼80 K between the two wells, suggesting a coupling between superconducting fluctuations and nonlinear phonons.
- Received 29 March 1990
DOI:https://doi.org/10.1103/PhysRevLett.65.1675
©1990 American Physical Society