Pomeranchuk and other instabilities in the t-t′ Hubbard model at the Van Hove filling -: art. no. 094516

We present a stability analysis of the two-dimensional t-t' Hubbard model for various values of the next-nearest-neighbor hopping t', and electron concentrations close to the Van Hove filling by means of the flow equation method. For t'greater than or equal to-t/3 a d(x)(2)-y(2)-wave Pomeranchuk instability dominates (apart from antiferromagnetism at small t'). At t'<-t/3, the leading instabilities are a g-wave Pomeranchuk instability and p-wave particle-hole instability in the triplet channel at temperatures T<0.15t, and an s*-magnetic phase for T>0.15t; upon increasing the electron concentration, the triplet analog of the flux phase occurs at low temperatures. Other weaker instabilities are also found.