We study signatures of superconductivity in a two-leg “checkerboard” Hubbard ladder model, defined as a one-dimensional (period 2) array of square plaquettes with an intraplaquette hopping $t$ and interplaquette hopping $t^{\prime }$, using the density-matrix renormalization-group method. The highest pairing scale (characterized by the spin gap or the pair binding energy, extrapolated to the thermodynamic limit) is found for doping levels close to half-filling, $U\approx 6t$ and $t^{\prime }/t\approx 0.6$. Other forms of modulated hopping parameters, with periods of either one or three lattice constants, are also found to enhance pairing relative to the uniform two-leg ladder, although to a lesser degree. A calculation of the phase stiffness of the ladder reveals that in the regime with the strongest pairing, the energy scale associated with phase ordering is comparable to the pairing scale.

• Received 23 August 2010

DOI:https://doi.org/10.1103/PhysRevB.83.054508