SUPERCONDUCTING ORDER-PARAMETER AND THE PHONON PROFILE IN THE BISMUTHFAMILY OF COMPOUNDS

We discuss far infrared measurements of members of superconducting com pounds members of the bismuth family. We find discrete changes in the areas of first and second order phonon band profiles near the supercon ductor critical temperature a. These show a plateau at temperatures we ll above Tc. This behavior is coincident with the observation of the s uperconductor gap and polaron formation at temperatures well above Tc. We conclude that changes in the vibrational bands may be interpreted as a consequence of polaron condensation and thus, taken as evidence o f strong electron-phonon interactions in high Tc superconductors.