Random Bond Effect in the Quantum Spin System

Yoshihiko Nonomura, Hidetoshi Nishimori, 野々村 喜彦 +1 more

Hongwei Fan, Zhaoxin Xu, He-Ping Ying

The effects of bond randomness on the quantum mixed-spin chain 1-1-1/2-1/2 are investigated by a quantum Monte Carlo study. We find that around the critical point of original pure system, quantum Griffiths phases appears, and its region is enlarged with increasing of bond randomness. Moreover, the critical behavior of the original quantum critical point has been changed by the randomness.

Abel Klein

Anders W. Sandvik

A Monte Carlo method for finite-temperature studies of the two-dimensional quantum Heisenberg antiferromagnet with random ferromagnetic bonds is presented. The scheme is based on an approximation which allows for an analytic summation over the realizations of the randomness, thereby significantly alleviating the ``sign problem'' for this frustrated spin system. The approximation is shown to be very accurate for ferromagnetic bond concentrations of up to 10%. The effects of a low concentration of ferromagnetic bonds on the antiferromagnetism are discussed.

Yutaka Okabe, Kazuhisa Kaneda, Yusuke Tomita +5 more

Kun Yang, R. A. Hyman, R. N. Bhatt +1 more

The effects of bond randomness are studied for spin chains with excitation gaps in the pure case. Systems with enforced topological structure like the spin-1/2 chain with enforced dimerization and spin-1 chain in the Haldane gapped phase appear very stable against randomness. On the other hand, systems with spontaneously generated topological order like the spin-1/2 chain with spontaneous dimerization are found to be unstable even for weak randomness despite the gap.