  The two-leg Hubbard ladder is characterized by the ratio of the inter- to
intra-leg hopping t_perp/t, the relative interaction strength U/t and the
electron filling. Here, using density matrix renormalization group and Monte
Carlo simulations, we examine the dependence of the pairing correlations on
these parameters. We find that the pairing correlations are enhanced when the
top of the bonding quasiparticle band and the bottom of the antibonding band
are near the Fermi level. We present results on the single-particle spectral
weight and the antiferromagnetic correlations in order to explain this
behavior.
