Electron-doping versus hole-doping in the 2D t-t ' Hubbard model

We compare the one-loop renormalization group flow to strong coupling of th e 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-do ped case with decreasing electron density there is a rapid transition from a d(x2-y2)-wave superconducting regime with small characteristic energy sca le to an approximate nesting regime with strong antiferromagnetic tendencie s and higher energy scales. This contrasts with the hole-doped side discuss ed recently which exhibits a broad parameter region where the renormalizati on group flow suggests a truncation of the Fermi surface at the saddle poin ts. We compare the quasiparticle scattering rates obtained from the renorma lization group calculation which further emphasize the differences between the two cases.