Soft phonon mode in the high-Tcsuperconductor Tl-Ba-Ca-Cu-O

Abstract
Thermal diffuse scattering due to a transverse phonon (e∥[010]) propagating along the [100] direction was found in electron-diffraction patterns of Tl-Ba-Ca-Cu-O with Tc of 117 K. The scattering has an intensity maximum at the middle between two fundamental spots along the 〈100〉 directions and its intensity increases with decreasing temperature. That is, the Tl oxide with high Tc exhibits the soft-phonon behavior.