Doped t-J model on a triangular lattice:: Possible application to NaxCoO2•yH2O and Na1-xTiO2 -: art. no. 092504

We report the finding of time-reversal-symmetry-breaking d(x)(2)-y(2)+id(xy) superconducting ground state in the slave-boson mean-field theory for the t-J model on triangular lattice. For t/J=-5(t/J=-9) pairing exists for x<13% (x<8%) upon electron doping, and x<56% (x<13%) upon hole doping. These results are potentially relevant to doped Mott insulators NaxCoO2.yH(2)O and Na1-xTiO2.