We show that the Fermi surfaces of the doped holes in the spin-liquid state consist of pairs of pockets separated by crystal momentum Q, in the low-doping limit. Due to the pocketlike structure of the Fermi surface and the A-B sublattice pairing, the spin-singlet superconducting order parameters have unusual symmetry properties. The order parameters are found to have nontrivial quantum numbers of 90° rotation and, sometimes, nonzero crystal momenta. The nonzero crystal momenta carried by the order parameters can be detected by measuring the unusual values (e.g., hc/4e) of the flux confined to various dislocations in superconducting thin films.

• Received 13 October 1989

DOI:https://doi.org/10.1103/PhysRevB.41.4212