Variational Monte Carlo study of pairing symmetries of Na0.3CoO2.1.3H2O*

To investigate possible pairing symmetries of Na0.3CoO2.1.3H2O, we study the single band extended Hubbard model on triangular lattice with variational Monte Carlo method. For the on site s-wave, the extended s-wave, the d-wave, the f-wave and the extended-f wave parings, we use the corresponding BCS type mean field wave functions with Jastrow factors as our trial wave functions. We found that in a suitable parameters region, the extended f-wave pairing is stabilized by the nearest-neighbor Coulomb interaction V. In order to further investigate the true ground state of this system we use the constrained path Monte Carlo (CPMC) method to calculate different correlation function in the ground state.