Anomalous Periodicity of the Current-Phase Relationship of   Grain-Boundary Josephson Junctions in High-Tc Superconductors
  The current-phase relation (CPR) for asymmetric 45 degree Josephson junctions between two d-wave superconductors has been predicted to exhibit an anomalous periodicity. We have used the single-junction interferometer to investigate the CPR for this kind of junctions in YBCO thin films. Half-fluxon periodicity has been experimentally found, providing a novel source of evidence for the d-wave symmetry of the pairing state of the cuprates. 
E. Il'ichev, V. Zakosarenko, R.P.J. IJsselsteijn, H. E. Hoenig, V.   Schultze, H.-G. Meyer, M. Grajcar, R. Hlubina