Electron-doping versus hole-doping in the 2D t-t′ Hubbard model

We compare the one-loop renormalization group flow to strong coupling of the electronic interactions in the two-dimensional t-t ' -Hubbard model with t ' = -0.3t for band fillings smaller and larger than half-filling. Using a numerical N-patch scheme (N = 32, ..., 96) we show that in the electron-doped case with decreasing electron density there is a rapid transition from a d(x2-y2)-wave superconducting regime with small characteristic energy scale to an approximate nesting regime with strong antiferromagnetic tendencies and higher energy scales. This contrasts with the hole-doped side discussed recently which exhibits a broad parameter region where the renormalization group flow suggests a truncation of the Fermi surface at the saddle points. We compare the quasiparticle scattering rates obtained from the renormalization group calculation which further emphasize the differences between the two cases.