TUNNELING SPECTRUM INDICATING PHONON CONTRIBUTION TO HIGH T-C OXIDE SUPERCONDUCTIVITY

Improved tunneling spectroscopy with [BSCCO(2212)/SiOx]/Lambda u tip p oint contact junction enables us to observe significant peaks in the t unneling conductance derivative spectrum d(2)l/d(2)V - V. Their peak e nergy eV(i) could be systematically assigned by cV(i) - Delta = n epsi lon(o) + h omega(i)(ph) with n=0,1,2. Here, <(h)over bar omega(i)> mea ns each phonon mode energy and epsilon(o)=72meV was found just corresp onding to the breathing mode of the Cu-O bond stretching i the CuO2 pl ane, which indicates that these characteristic optical phonons play an essential role in the high T-c superconductivity. The infrared reflec tance spectrum by Capizzi et al. on similar substance is found in peak correspondence.