Possible coexistence of superconductivity and static SDW stripes in the two-dimensional Hubbard model Original Research Article

The possibility of superconductivity coexisting in the stripe state of spin-density-wave (SDW) is studied by using the variational Monte Carlo method as the ground state of the under-doped two-dimensional (2D) Hubbard model. The model parameters are chosen for cuprate high-Tc superconductors such as La2−xSrxCuO4 with x<0.125. We show that the total energies of the inhomogeneous d-wave superconducting (SC) states with vertical stripes having 8-, 10- and 12-lattice periodicities are lower than those of competing SDW states. With decreasing hole doping, the interval of stripes increased in good agreement with the experimental x-dependence of incommensurability. The decreasing tendency of the condensation energy with decreasing doping is in accord with that of the specific heat data.