Unconventional superconducting states on doped Shastry-Sutherland lattice

Abstract

By using a renormalized mean-field theory, we investigate the phase diagram of $t$-$t^{\prime }$-$J$-$J^{\prime }$ model on two dimensional Shastry-Sutherland lattice which are topologically equivalent to synthesized material $\mathrm{SrC}{\mathrm{u}}_2(\mathrm{B}{\mathrm{O}}_3{)}_2$. We find that the symmetry of superconductivity ground state depends on the frustration amplitude $\eta =t^{\prime }/t$ and doping concentration. For weak to intermediate frustration, $d_{x^2-y^2}$-wave pairing symmetry is robust in a large parameter region. Around the symmetric point $|\eta |=1$, d-wave, $s$-s-wave pairing as well as staggered flux may serve as ground state by varying the doping level. There is a first-order transition between these distinct ground states. For larger frustration $|\eta |>1$, the ground state has an $s$-s-wave symmetry for both hole and electron doping.

6 pages, 7 figures