arXiv:cond-mat/0206092 · Physical review. B, Condensed matter
Ground state of the random-bond spin-1 Heisenberg chain
Sara Bergkvist, Patrik Henelius, Anders Rosengren
Abstract
Stochastic series expansion quantum Monte Carlo is used to study the ground state of the antiferromagnetic spin-1 Heisenberg chain with bond disorder. Typical spin- and string-correlation functions behave in accordance with real-space renormalization group predictions for the random-singlet phase. The average string-correlation function decays algebraically with an exponent of $\ensuremath{-}0.378(6),$ in very good agreement with the prediction of $\ensuremath{-}(3\ensuremath{-}\sqrt{5})/2\ensuremath{\simeq}\ensuremath{-}0.382,$ while the average spin-correlation function is found to decay with an exponent of about $\ensuremath{-}1,$ quite different from the expected value of $\ensuremath{-}2.$ By implementing the concept of directed loops for the spin-1 chain we show that autocorrelation times can be reduced by up to two orders of magnitude.