Spin susceptibilities of a one-dimensional disordered quantum Heisenberg antiferromagnet

We have calculated, using quantum Monte Carlo simulations, various spin susceptibilities of a one-dimensional disordered isotropic Heisenberg antiferromagnet (s=(1/2)). We find that in the low-temperature limit the q=0 spin susceptibility begins to diverge as was predicted theoretically several years ago with use of renormalization-group calculations. We also find that the q={π} spin susceptibility is suppressed in the presence of disorder, but the susceptibility associated with the spin-Peierls instability is enhanced by the disorder. We discuss the possible relevance of our results to experiments on quinolinium di-tetracyanoquinodimethane [Qn(TCNQ)₂], and suggest that it may be an example of a random spin-Peierls system.