A theoretical investigation of boson versions of the t-J and t-Jz models on the square lattice is carried out, by means of Green's function Monte Carlo simulations. Accurate ground-state energy estimates as a function of hole doping are obtained, allowing one to investigate the stability of the uniform phase against separation of the system into hole-rich and hole-free phases. In the boson t-Jz model, such a separation is found to occur for arbitrarily small values of Jz, at sufficiently low hole doping. Phase separation is suppressed in the boson t-J model, which features a uniform ground state at any doping, for J/t<~1.5. Relevance of this study to the corresponding fermion models is discussed. Fermi statistics enhances the tendency toward phase separation; in particular, phase separation at low doping is predicted in the fermion t-Jz model at any Jz>0. The possible formation of stripes of holes is investigated for systems featuring both periodic and cylindrical boundary conditions. No evidence of a striped ground state is found in either the t-J or t-Jz boson models.
Physical Review B
- Pub Date:
- April 2002
- Magnetic phase boundaries;
- Mixed systems;
- liquid <sup>3</sup>He <sup>4</sup>He mixtures;
- Computer simulation of liquid structure;