The Doped Two-Chain Hubbard Model

The properties of the two-chain Hubbard model doped away from half-filling are investigated with the density matrix renormalization group. The charge gap is found to vanish, but a finite spin gap phase exists over a range of interchain hopping strength t ⊥ . In this phase, there are modified d x 2 - y 2 pairing correlations which exhibit a power law decay while both the 2 k F spin and charge correlations are short range. Above a critical value of t ⊥ , the system behaves as a Luttinger liquid.