C. Honerkamp et M. Salmhofer, Magnetic and superconducting instabilities of the Hubbard model at the VanHove filling - art. no. 187004, PHYS REV L, 8718(18), 2001, pp. 7004
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.