Tunneling spectrum indicating phonon contribution to high t_c oxide superconductivity

Improved tunneling spectroscopy with [BSCCO(2212)/SiO₂]/Au, tip point contact junction enables us to observe significant, peaks in the tunneling conductance derivative spectrum d²t/d²V - V. Their peak energy eV_i could be systematically a.ssigoed by eV_i-Δ = nε₀ + hw_i (ph) with n=0,1,2, Here, hw_i means each phonon mode energy and ε₀ = 72me V was found just corresponding to the breathing mode of the Cu-O bond stretching in the Cue2 plane, which iudicates that these characteristic optical phonons play an essential role in the high T_c superconductivity. The infrared reflectance spectrum by Capizzi et al. on similar substance is found in peak correspondence.