Tricrystal Tests of Pairing Symmetry in Cuprate Superconductors

Influence of twin boundaries on Josephson junctions between high-temperature and conventional superconductors

“…We also emphasize that the other case would lead to a conflict in the interpretation of the SQUID and loop experiments mentioned above, where it is assumed that twinning does not affect the basal plane Josephson coupling along the main axes. 7,8,21,22 Our assumption for the behavior of d leads to a situation where the respective sign of the pair wave function along both main axis is the same in all twin domains.…”

“…This new flux quantization has been observed recently and fits also well into the picture of a d-wave superconductor. 8 Further support for d-wave symmetry comes from the modification of Fraunhofer interference patterns for weak Josephson junctions at a corner of a YBCO crystal. 9 Nevertheless, these results have been challenged by two other experiments based on the idea of the probing Josephson couplings ''forbidden'' by symmetry.…”

Scanning SQUID microscopy of sparsely twinnedYBa2Cu3Moler1, Kirtley2, Liang3 et al. 1997Phys. Rev. B440263View full textAdd to dashboardCite

“…Several phase-sensitive Josephson experiments demonstrate the existence of a sign change in the order parameter of YBCO, 5,[12][13][14][15] including tunneling experiments in Pb-YBCO corner junctions in which the phase change is inferred from the critical current, 13 and imaging experiments which show half-integral flux quanta in tricrystal geometries of YBCO. 5,12 These experiments point towards the particular pairing symmetry d x 2 Ϫy 2. 16 There are also c-axis tunneling experiments, however, in which the detection of first-order tunneling in a c-axis YBCO-Pb junction seems to indicate that the order parameter of YBCO cannot be purely d wave.…”

Mechanism for magnetic-flux generation in grain boundaries ofYBa2Cu3Walker1 1996Phys. Rev. B3020View full textAdd to dashboardCite

“…Since the Josephson experiments on twinned crystals [12][13][14][15][16][17] show macroscopic d x 2 Ϫy 2 symmetry, the superconducting twin boundaries must have odd reflection symmetry. Further details of this argument can be found in Refs.…”