Temperature dependence of the phonon structure in the high-temperature superconductor BI2SR2CACU2O8 studied by infrared reflectance spectroscopy

We have investigated a ceramic sample of the high-temperature superconductor Bi2Sr2CaCu2O8 (T(c) = 85 K) by infrared and visible reflectance spectroscopy at several temperatures both below and above the superconducting transition. We find that the temperature variation in the vibrational region is associated with minima or antiresonance features of the optical conductivity, instead of maxima, indicating strong Fano-type electron-phonon interaction and implying that the phonon structure in the infrared is strongly affected by the ab-plane response