Density matrix renormalization group study of random dimerized antiferromagnetic Heisenberg chain

Abstract

The effect of dimerization on the random antiferomagnetic Heisenberg chain with spin ½ is studied using the density matrix renormalization group method. The ground-state energy, the energy gap distribution and the string-order parameter are calculated and analyzed using the finite size scaling method. The ground-state energy gain due to dimerization behaves as u a with a ≳ 2, where u is the degree of dimerization, suggesting the absence of spin-Peierls instability. The string order is found to behave as u 2β with β ∼ 0.35 in contrast to the prediction of real space renormalization group theory.