Evidence for electron-phonon interaction in Bi2Sr2CaCu2O8+x from tunneling measurements

Abstract Tunneling effects in Bi 2 Sr 2 CaCu 2 O 8+x single crystals with Tc=80÷90K have been investigated using a break junction technique. A reproducible fine structure has been observed in the tunneling spectrum at voltages V > Vg=2Δ/e, which shifts with the gap feature to lower voltages with increasing temperature. This structure correlates with the phonon density of states, as determined by inelastic neutron scattering, and indicates the importance of electron-phonon interaction for the superconductivity in BiSrCaCuO.