Possible two-component spin-singlet pairings in Sr2RuO4

Recent experiments suggest a multi-component pairing function in Sr2RuO4, which appears to be inconsistent with the absence of an apparent cusp in the transition temperature (Tc) as a function of the uniaxial strain. We show, however, that the theoretical cusp in Tc for a multi-component pairing can be easily smeared out by the spatial inhomogeneity of strain, and the experimental data can be reproduced qualitatively by a percolation model. This shed new light on multi-component pairings. We then perform a thorough group-theoretical classification of the pairing functions, taking the spin-orbit coupling into account. We list all 13 types of two-component spin-singlet pairing functions, with 8 of them belonging to the Eg representation. In particular, we find two types of intra-orbital pairings in the Eg representation ($k_xk_z$, $k_yk_z$) are favorable in view of most existing experiments.