Superconductivity and density-wave fluctuations in an extended triangular Hubbard model: an application to SnSe 2 .

We employ the fluctuation-exchange approximation to study the relation of superconducting pairing symmetries and density-wave fluctuations based on the extended triangular Hubbard model upon electron doping and interactions, with an possible application to the layered metal dichalcogenide SnSe 2 . For the case where the interactions between electrons contain only the on-site Hubbard term, the superconducting pairings are mainly mediated by spin fluctuations, and the spin-singlet pairing with the d -wave symmetry robustly dominates in the low and moderate doping levels, and a d -wave to extended s -wave transition is observed as the electron doping reaches n  = 1. When the near-neighbor site Coulomb interactions are also included, the charge fluctuations are enhanced, and the spin-triplet pairings with the p -wave and f -wave symmetries can be realized in the high and low doping levels, respectively.