arXiv:cond-mat/9711125 · Physical review. B, Condensed matter
Quantum Monte Carlo study of hole binding and pairing correlations in the three-band Hubbard model
M. Guerrero, James E. Gubernatis, Shiwei Zhang
Abstract
We simulated the three-band Hubbard model using the constrained-path Monte Carlo (CPMC) method in search for a possible superconducting ground state. The CPMC is a ground-state method that is free of the exponential scaling of computing time with system size. We calculated the binding energy of a pair of holes for systems up to $6\ifmmode\times\else\texttimes\fi{}4$ unit cells. We also studied the pairing correlation functions versus distance for both the $d$-wave and extended $s$-wave channels in systems up to $6\ifmmode\times\else\texttimes\fi{}6$. We found that holes bind for a wide range of parameters and that the binding increased as the system size is increased. However, the pairing correlation functions decay quickly with distance. For the extended $s$ channel, we found that as the Coulomb interaction ${U}_{d}$ on the Cu sites is increased, the long-range part of the correlation functions is suppressed and fluctuates around zero. For the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ channel, we found that the correlations decay rapidly with distance towards a small positive value. However, this value becomes smaller as the interaction ${U}_{d}$ or the system size is increased.