Low-temperature properties of the random Heisenberg antiferromagnetic chain

The one-dimensional quantum spin-½ Heisenberg antiferromagnetic model with randomly distributed interaction strengths is solved approximately for several different distributions. Ground-state energy and low-temperature properties are evaluated. Universal qualitative features are found in the specific heat and the magnetic susceptibility, which display a power-law dependence on temperature. Such features hold for nonsingular distributions as well as for distributions with power-law divergence at the origin. The approximate method of solution is based on successive eliminations of spins coupled by the maximum coupling constant.