Ground state energy density, susceptibility, and Wilson ratio of a two-dimensional disordered quantum spin system
Abstract
A two-dimensional (2D) spin-1/2 antiferromagnetic Heisenberg model with a specific kind of quenched disorder is investigated, using the first principles nonperturbative quantum Monte Carlo calculations (QMC). The employed disorder distribution has a tunable parameter p which can be considered as a measure of the corresponding randomness. In particular, when p=0 the disordered system becomes the clean one. Through a large scale QMC, the dynamic critical exponents z, the ground state energy densities E0, as well as the Wilson ratios W of various p are determined with high precision. Interestingly, we find that the p dependence of z and W are likely to be complementary to each other. For instance, while the z of 0.4 p 0.9 match well among themselves and are statistically different from z=1 which corresponds to the clean system, the W for p < 0.7 are in reasonable good agreement with that of p=0. The technical subtlety of calculating these physical quantities for a disordered system is demonstrated as well. The results presented here are not only interesting from a theoretical perspective, but also can serve as benchmarks for future related studies.