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 SrCu 2 (BO 3 ) 2 , Yb 2 Pt 2 Pb. 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.