Doping asymmetry in the three-band model for cuprate ladders

The validity of the two-dimensional one-band Hubbard model to the high temperature cuprate superconductivity remains controversial. The Hubbard ladder lattices are one of the models to precisely examine the difference between one- and multi-band models. While the ground state of the doped one-band ladder is known to be a Luther-Emery superconducting phase, recent results of the hole-doped three-band model found the rapid suppression of the superconducting phase for realistic cuprate parameters. Here we present density matrix renormalization group calculations for the electron-doped cuprate ladders over a wide range of doping levels. For electron doping we find the Luther-Emery superconductivity with quasi-long-range order. Our numerical results appear to be in agreement with recent studies on t-t'-J model that found strong pairing for positive t' (electron doping), but suppression of pairing for negative t' (hole doping). Our results demonstrate that the generic three-band model cannot be reduced to the effective Zhang-Rice model for hole doping.