Magnetic and superconducting instabilities of the Hubbard model at the VanHove filling - art. no. 187004

We use a novel temperature-flow renormalization group technique to analyze magnetic and superconducting instabilities in the two-dimensional t - t' Hu bbard model for particle densities close to the Van Hove filling as a funct ion of the next-nearest-neighbor hopping t'. In the one-loop flow at the Va n Hove filling, the characteristic temperature for the flow to strong coupl ing is suppressed drastically around t(c)' approximate to -0.33t, suggestin g a quantum critical point between d-wave pairing at moderate t' > t(c)' an d ferromagnetism for t' < t(c)'. Upon increasing the particle density in th e latter regime, the leading instability occurs in the triplet pairing chan nel.