MgB2 Energy Gap Determination by Scanning Tunneling Spectroscopy

Heitmann, T. W.; Bu, S. D.; Kim, D. M.; Choi, J. H.; Giencke, J.; Eom, C. B.; Regan, K. A.; Rogado, N.; Hayward, M. A.; He, T.; Slusky, J. S.; Khalifah, P.; Haas, M.; Cava, R. J.; Larbalestier, D. C; Rzchowski, M. S.

MgB2 Energy Gap Determination by Scanning Tunneling Spectroscopy

Authors

Description

We report scanning tunneling spectroscopy (STS) measurements of the gap properties of both ceramic MgB2 and c-axis oriented epitaxial MgB2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunneling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap delta=2.3-2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, delta=7.2 meV, consistent with a proposed two-band model.
24 pages, 8 figures Text changes and corrected fits in figures Submitted to Superconductor Science and Technology