We have measured the magnetic field modulation of the critical current of YBCO-Au-Pb Josephson junctions fabricated on the a and b edges and straddling the a-b corners of YBCO single crystals. In corner junctions, the critical current drops sharply at zero applied field and increases as the field is increased in either direction, in sharp contrast to the Fraunhofer diffraction patterns observed for single edge junctions. This behavior signifies a sign change of the order parameter between the a and b directions, strong direct evidence that the superconducting pairing state of YBCO has dx2-y2 symmetry.
ASJC Scopus subject areas
- Physics and Astronomy(all)