Classical correlation-length exponent in the nonuniversal quantum phase transition of a diluted Heisenberg antiferromagnet - art. no. 140415

Critical behavior of the quantum phase transition of a site-diluted Heisenb erg antiferromagnet on a square lattice is investigated by means of the qua ntum Monte Carlo simulation with the continuous-imaginary-time loop algorit hm. Although the staggered spin-correlation function decays in a power law with the exponent definitely depending on the spin size S, the correlation- length exponent is classical, i.e., v=4/3. This implies that the length sca le characterizing the nonuniversal quantum phase transition is nothing but the mean size of connected spin clusters.