Random bond XXZ chains with modulated couplings

Abstract

The magnetization behavior of q-periodic antiferromagnetic spin 1/2 Heisenberg chains under uniform magnetic fields is investigated in a background of disorder exchange distributions. By means of both real space decimation procedures and numerical diagonalizations in XX chains, it is found that for binary disorder the magnetization exhibits wide plateaux at values of 1+2(p-1)/q, where p is the disorder strength. In contrast, no spin gaps are observed in the presence of continuous exchange distributions. We also study the magnetic susceptibility at low magnetic fields. For odd q-modulations the susceptibility exhibits a universal singularity, whereas for q even it displays a non-universal power law behavior depending on the parameters of the distribution.

4 pages, 3 figures. Final version to appear in PRL

References in corpus (3)

• Density of states in coupled chains with off-diagonal disorder
• Random antiferromagnetic quantum spin chains: Exact results from scaling of rare regions
• Quantum Spin Systems: From Spin Gaps to Pseudo Gaps

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