@article{oai:sucra.repo.nii.ac.jp:00012524,
 author = {飛田, 和男},
 issue = {7},
 journal = {Journal of the Physical Society of Japan},
 month = {},
 note = {http://jpsj.ipap.jp/link?JPSJ/75/074709 | http://jpsj.ipap.jp/link?JPSJ/75/074709, The multiple reentrant quantum phase transitions in the S = 1/2 antiferromagnetic Heisenberg　chains with random bond alternation in the magnetic field are investigated by the density　matrix renormalization group method combined with interchain mean field approximation. It is　assumed that odd numbered bonds are antiferromagnetic with strength J and even numbered　bonds can take the values JS and JW (JS > J > JW > 0) randomly with the probabilities p and　1−p, respectively. The pure version (p = 0 and p = 1) of this model has a spin gap but exhibits　a field-induced antiferromagnetism in the presence of interchain coupling if Zeeman energy due　to the magnetic field exceeds the spin gap. For 0 < p < 1, antiferromagnetism is induced by　randomness at the small field region where the ground state is disordered due to the spin gap　in the pure version. At the same time, this model exhibits randomness-induced plateaus at　several values of magnetization. The antiferromagnetism is destroyed on the plateaus. As a　consequence, we find a series of reentrant quantum phase transitions between transverse antiferromagnetic　phases and disordered plateau phases with the increase of magnetic field for a　moderate strength of interchain coupling. Above the main plateaus, the magnetization curve　consists of a series of small plateaus and jumps between them. It is also found that antiferromagnetism　is induced by infinitesimal interchain coupling at the jumps between the small　plateaus. We conclude that this antiferromagnetism is supported by the mixing of low-lying　excited states by the staggered interchain mean field even though the spin correlation function　is short ranged in the ground state of each chain., Copyright(c)2006 The Physical Society of Japan, text, application/pdf},
 pages = {074709-1--074709-5},
 title = {Field-induced multiple reentrant quantum phase transitions in randomly dimerized antiferromagnetic S=1/2 Heisenberg chains},
 volume = {75},
 year = {2006},
 yomi = {ヒダ, カズオ}
}