Stripe states in t-t′-J model from a variational viewpoint

The stripe states discussed in the variational Monte Carlo simulations are reviewed. The interplay between stripes and d(x2-y2)-wave superconductivity in the two-dimensional t-t'-J model is emphasized. The next-nearest-neighbor hopping t' < 0 stabilizes the stripe states around the hole doping rate, delta = 1/8. It is found that the stripes and spatially oscillating superconductivity coexist depending on parameters. The superconductivity order parameter is enhanced at the hole stripe regions, and its sign becomes opposite on the adjacent hole stripes (i.e., antiphase). It is also found that the energy differences between homogeneous states and the stripe states with and without superconductivity are relatively small. We consider the possibility that the antiphase coexistence may explain the weakness of the c-axis Josephson couplings in some of the high-T-c cuprates. (C) 2012 Elsevier B. V. All rights reserved.