RANDOM BONDS AND TOPOLOGICAL STABILITY IN GAPPED QUANTUM SPIN CHAINS

Using an asymptotically exact real space renormalization procedure, we find that the dimerized spin-1/2 chain is extremely stable against bo nd randomness. For weak dimerization or, equivalently, strong randomne ss, it is in a Griffiths phase with short-range spin-spin correlations and a divergent susceptibility. The string topological order persists . We conjecture that random integer spin chains in the Haldane phase e xhibit similar thermodynamic and topological properties.