Angle-resolved tunneling study on the anisotropic gap of Bi-2212 superconducting whisker

A tunneling study was performed on the c-axis direction of the Bi-2212 superconducting whiskers with the superconducting transition temperature of 72 K. The contact junction method was adopted to fabricate the nanometer scale tunnel junction by using a native oxide barrier on the whisker surface. We carried out the angle-resolved tunneling measurements at 7.1 K by rotating the probe whisker over the sample whisker. We find that the superconducting gap energy of Bi-2212 superconductor is strongly dependent on the rotating angle, reflecting the d-wave symmetry of the Cooper pair wave function. q1999 Elsevier Science B.V. All rights reserved.