Monte Carlo studies of magnetism and superconductivity on the triangular lattice

To study the magnetic and superconducting properties of the Na(x)CoO(2)center dot yH(2)O materials, we perform quantum Monte Carlo calculation on the single-band Hubbard model on a triangular lattice. Through the observation of magnetic susceptibility as a function of electron filling and temperature, it is interesting to see that the ferromagnetic fluctuation dominates in the high-filling region < n >=1.5-1.85 and competes with the antiferromagnetic fluctuation in the filling region < n >similar to 1.33. We also observe that triplet pairing is favorable around the ferromagnetic region, and the f-wave pairing correlation tends to increase faster with decreasing temperature than other pairing channels. (C) 2008 American Institute of Physics.