title: Phase diagram of the random Heisenberg antiferromagnetic spin-1 chain.
abstract: We present a new perturbative real space renormalization group (RG) to study random quantum spin chains and other one-dimensional disordered quantum systems. The method overcomes problems of the original approach which fails for quantum random chains with spins larger than S=1/2. Since it works even for weak disorder, we are able to obtain the zero temperature phase diagram of the random antiferromagnetic Heisenberg spin-1 chain as a function of disorder. We find a random singlet phase for strong disorder. As the disorder decreases, the system shows a crossover from a Griffiths to a disordered Haldane phase.
authors.affiliation: Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150 Urca, Rio de Janeiro, 22290-180 RJ, Brazil.
authors.forename: Andreia
authors.initials: A
authors.lastname: Saguia
authors.forename: Beatriz
authors.initials: B
authors.lastname: Boechat
authors.forename: Mucio A
authors.initials: MA
authors.lastname: Continentino