Unconventional superconducting states on doped Shastry-Sutherland lattice
Abstract 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 η = t ′ / t and doping concentration. For weak and intermediate |η|, d x 2 − y 2 -wave superconducting state is robust in a wide region. While for larger |η| > 1 cases, the superconducting ground state has s–s-wave symmetry. Around the most frustrated η = ± 1 point, d x 2 − y 2 -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.