Observation of Bound Surface States in Grain Boundary Junctions of High Temperature Superconductors

Abstract

We have performed a detailed study of the tunneling spectra of bicrystal grain boundary junctions (GBJs) fabricated from the HTS YBCO, BSCCO, LSCO, and NCCO. In all experiments the tunneling direction was along the CuO planes. With the exception of NCCO, for all materials a pronounced zero bias conductance peak was observed which decreases with increasing temperature and disappears at the critical temperature. These results can be explained by the presence of a dominating d-wave symmetry of the order parameter resulting in the formation of zero energy Andreev bound states at surfaces and interfaces of HTS. The absence of a ZBCP for NCCO is consistent with a dominating s-wave symmetry of the pair potential in this material. The observed nonlinear shift of spectral weight to finite energies by applying a magnetic field is in qualitative agreement with recent theoretical predictions.

4 pages, 4 figures, to be published in Phys. Rev. B

References in corpus (4)

• Tunneling into Current-Carrying Surface States of High T${}_c$ Superconductors
• Fractional Vortices as Evidence of Time-Reversal Symmetry Breaking in High-Temperature Superconductors
• Charge Transport in Junctions between D-Wave Superconductors
• The Effect of Surfaces on the Tunneling Density of States of an Anisotropically Paired Superconductor

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