Anomalous magnetic-field tunneling of YBa2Cu3O7-δ junctions:: Possible detection of non-Fermi-liquid states -: art. no. 094501

Magnetic-field tunneling spectroscopy was applied to optimally doped YBa2Cu3O7-delta (YBCO) to detect the quasiparticle properties in the superconducting phase. Three types of epitaxial YBCO/La0.67Sr0.33MnO3 junctions with different orientations were fabricated, and the responses of conductance spectra to an applied parallel magnetic field were measured at below 1 K. The measured conductance spectra showed neither splitting nor broadening with muV resolution. This result apparently contradicts the model based on the weak coupling theory. One possibility for this contradiction is the breakdown of the superconducting Fermi-liquid in optimally doped YBCO.