Zero-bias anomaly in the tunneling spectroscopy of high-Tc superconducting films

Abstract

The Coulomb staircase structure observed in the tunneling current-voltage characteristics (IVC's) of superconducting YBa2Cu3O7-delta(YBCO) films have been found to exhibit an extra feature of zero-bias anomaly (ZBA), with Delta V-0 approximate to 1.5 Delta V-n when the bias voltage exceeded a certain threshold value. Where Delta V-0 and Delta V-n (which remains essentially constant) are the widths of the voltage step across zero bias and other higher order steps, respectively. Comparisons made with TlBa2Ca2Cu3O9+/-delta (Tl-1223) films under similar conditions indicate that the effects of surface layer polarization might be the primary reason responsible for the ZBA observed in YBCO films.