Tunneling spectroscopy in Ba1-xKxBiO3

Tunneling measurements have been performed on bulk samples of Ba1-xKxBiO3 for x = 0.375 to 0.5 using the natural, surface oxide as the tunnel barrier. High bias conductance and second derivative measurements show features in the energy range 10 to 65 meV which are characteristic of phonon effects as seen in conventional superconductors. The structures appear at energies which correspond to peaks in the phonon density of states as measured by inelastic neutron scattering and Raman spectroscopy. These results indicate that phonon-mediated pairing is responsible for superconductivity in this compound