Magnetic and superconducting instabilities of the Hubbard model at the van Hove filling

Abstract

We use a novel temperature-flow renormalization group technique to analyze magnetic and superconducting instabilities in the two-dimensional t-t&#39; Hubbard model for particle densities close to the van Hove filling as a function of the next-nearest neighbor hopping t&#39;. In the one-loop flow at the van Hove filling, the characteristic temperature for the flow to strong coupling is suppressed drastically around t&#39;_c approx. -0.33t, suggesting a quantum critical point between d-wave pairing at moderate t&#39;>t&#39;_c and ferromagnetism for t&#39;<t&#39;_c. Upon increasing the particle density in the latter regime the leading instability occurs in the triplet pairing channel.