Tunnel-like characteristics of YBa2Cu3O7-y/CeO2/YBa2Cu3O7-y junctions and possible evidence of excitations responsible for high-Tc superconductivity.

The tunnel-like characteristics observed in YBa 2 Cu 7-y /CeO 2 /YBa 2 Cu 3 O 7-y heteroepitaxial junctions fabricated by a vacuum evaporation technique are reported. Pronounced gaplike structures around 9 and 20 mV, which depend on temperature and the additional structures at high-bias voltages (40-180 mV), are observable. The latter structures emerge rapidly near T c and may reflect the density of states of the possible excitations responsible for high-T c superconductivity. The data suggest that the excitations other than phonons are possible