T. Hikihara et al., Numerical renormalization-group study of spin correlations in one-dimensional random spin chains, PHYS REV B, 60(17), 1999, pp. 12116-12124
We calculate the ground-state two-spin correlation functions of spin-1/2 qu
antum Heisenberg chains with random exchange couplings using the real-space
renormalization-group scheme. We extend the conventional scheme to take ac
count of the contribution of local higher multiplet excitations in each dec
imation step. This extended scheme can provide highly accurate numerical da
ta for large systems. The random average of staggered spin correlations of
the chains with random antiferromagnetic (AF) couplings shows algebraic dec
ay like 1/r(2), which verifies the Fisher's analytic results. For chains wi
th random ferromagnetic (FM) and AF couplings, the random average of genera
lized staggered correlations is found to decay more slowly than a power law
, in the form close to 1/ln(r). The difference between the distribution fun
ctions of the spin correlations of the random AF chains and of the random F
M-AF chains is also discussed. [S0163-1829(99)04941-3].