Experimental test for subdominant superconducting phases with complex order parameters in cuprate grain boundary junctions.
We propose and implement a direct experimental test for subdominant superconducting phases with broken time-reversal symmetry in d-wave superconductors. The critical current of 45 degrees -asymmetric grain boundary junctions is shown to be extremely sensitive to the predicted onset of a complex order parameter at (110) surfaces and near magnetic impurities. Measurements in pure Ni-doped YBa2Cu3O7-x junctions indicate that the symmetry at the surface is consistent with pure d-wave at all temperatures, putting limits on the magnitude and chiral domain structure of any subdominant symmetry component.
Neils
W K
WK
Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, Illinois 61801, USA.
Van Harlingen
D J
DJ