Unconventional superconducting states on doped Shastry-Sutherland lattice

By using a renormalized mean-field theory, we investigate the phase diagram of t-t'-J-J' model on a two dimensional Shastry-Sutherland ( SS) lattice which can be realized in a group of layered compounds such as SrCu2(BO3)(2), Yb2Pt2Pb. We find that the symmetry of ground state depends on frustration parameter eta = t'/t and doping concentration. For weak and intermediate vertical bar eta vertical bar , d(x2-y2)-wave superconducting state is robust in a wide region. While for larger vertical bar eta vertical bar > 1 cases, the superconducting ground state has s-s-wave symmetry. Around the most frustrated eta = +/- 1 point, d(x2-y2)-wave state, s-s-wave state as well as staggered-flux state appear, the energy favorable state is the ground state. The order of the phase transition between different states depends on the continuity of the mean field order parameters. (C) 2016 Elsevier B. V. All rights reserved.