Sound Velocity and Attenuation in YBa2Cu3Oy

Abstract
The sound velocity and attenuation in a sintered single phase YBa2Cu3O6.9 (denoted as orthor-I), which has a superconducting transition temperature, T c of about 90 K, were measured and compared with those of the corresponding semiconductor YBa2Cu3O6.2 (denoted as tetra-II). The sound velocity in ortho-I has an additional increase below T c, in contrast to that of tetra-II. This anomaly may imply a strong coupling between the lattice and electrons in this system. This cannot be explained by a simple thermodynamic analysis. The sound attenuation does not show any anomaly around T c.