We report sound-velocity measurements on polycrystalline single-phase YBa2Cu3O7 with a Tc of 90 K. The sound velocity is found to increase as the temperature is reduced from room temperature in contrast to the decrease observed in La1.85Sr0.15CuO4. At Tc there is no discontinuity in the sound velocity within experimental resolution, as expected from thermodynamic arguments and the small value of dTcdP. As the temperature is lowered below Tc the sound velocity increases at a greater rate. A similar increase below Tc is observed in La1.85Sr0.15CuO4. The magnitude of the sound-velocity increase below Tc is much larger than observed in conventional superconductors.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics