Temperature dependence of CDW and d-wave pair correlations in the 2D extended Hubbard model

Using the auxiliary field quantum Monte Carlo (QMC) method, we study the root 2 x root 2 charge density wave (CDW) and d-wave pair correlation functions of the square-lattice extended Hubbard model with intersite Coulomb repulsions. We confirm the existence of a finite-temperature CDW transition which belongs to the 3D Ising universality class at half filling and near half filling. We also find that the hole doping leads to only slight suppression of the CDW transition temperature, which indicates robustness of the CDW ordering. As for pairing correlations, it is found that the d(xy)-wave correlation increases rapidly when the CDW ordering appears, although we do not succeed in detecting the long-range superconducting order within temperature range in our calculations. (c) 2006 Elsevier B.V. All rights reserved.