Instabilities of interacting electrons on the triangular lattice

Motivated by the recent finding of superconductivity in layered CoO2 compounds, we investigate superconducting and magnetic instabilities of interacting electrons on the two-dimensional triangular lattice. Using a one-loop renormalization-group scheme for weak- to moderate-coupling strengths, we find that for purely local interactions U>0 and small Fermi surfaces the renormalization-group flow remains bounded down to very low scales and no superconducting or other instabilities can be detected. Antiferromagnetic exchange interactions J generate a wide density region with a d(x)(2)-y(2)+id(xy)-wave superconducting instability similar to recent proposals for the strongly correlated t-J model. For larger Fermi-surface volumes the interactions flow to strong coupling also for purely local interactions U>0. We find a singlet-pairing instability in the vicinity of strong magnetic ordering tendencies at three wave vectors for the Van Hove filling.