The Superconducting d-wave Pairing and Antiferromagnetic Order on the Coupled Hubbard Ladders: A Quantum Monte Carlo Study

Using determinant quantum Monte Carlo algorithm, we study the superconducting d-wave pairing and antiferromagnetic order on the coupled Hubbard ladders. With the presence of the next-nearest-neighbor hopping t' = -0.25, we find that, when the hopping strength among ladders decreases, the d-wave pairing is firstly enhanced and then gets suppressed, showing an optimal hopping inhomogeneity for the d-wave pairing. Without the next-nearest-neighbor hopping, however, the d-wave pairing is suppressed monotonically, i.e., no optimal inhomogeneity exists. We also measure the antiferromagnetic structure factor, which also presents an optimal inhomogeneity with the next-nearest-neighbor hopping t' = -0.25, and no such optimal inhomogeneity when t' = 0.0. The effect of different temperature, interaction strength, electron density, and lattice size is carefully studied and discussed.