Monte carlo study of correlations in quantum spin ladders

We study antiferromagnetic spin-1/2 Heisenberg ladders, comprised of nc chains [Formula presented] with ratio [Formula presented] of interchain to intrachain couplings. The correlation length ξ(T) is deduced from measurements of the correlation function. For even nc, the static structure factor exhibits a peak at a temperature below the corresponding spin gap. Results for isotropically coupled ladders [Formula presented] are compared to those for the single chain and the square lattice. For [Formula presented], the correlation function of the two-chain ladder is in excellent agreement with analytic results from conformal field theory, and ξ(T) exhibits simple scaling behavior.