RAMAN-ACTIVE PHONON SOFTENING IN A TL-BA-CA-CU-O SUPERCONDUCTING THIN-FILM

We report on a Raman scattering study of a large-area spray pyrolysed TlBaCaCuO superconducting thin film (Tc = 111 K). We have analysed the temperature dependence of the lineshape of the apical and bridging oxygen vibration (A1g) modes taken from an intimate mixture of TBCCO-1223 and -2223 crystallites and have found evidence for anomalous phonon self-energy effects at or near the critical transition temperature. Possible mechanisms that could account for this behaviour are discussed. © 1995