Models of Superconductivity in Sr_2RuO_4

Recent experimental data on purest Sr_2RuO_4 single crystals clearly indicate the presence of nodes in the superconducting order parameter. Here, we consider one special p-wave order parameter symmetry and two two-dimensional f-wave order parameter symmetries having nodes within the RuO_2 plane. These states reasonably describe both specific heat and penetration depth data. We calculate the thermal conductivity tensor for these three states and compare the results with recent thermal conductivity data. This allows us to single out one of these states being consistent with both thermodynamic and thermal conductivity data: the planar f-wave state having B_{1g} x E_u symmetry.