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arXiv:cond-mat/0007219 · Journal of the Physical Society of Japan

Dynamical Structure Factors of theS=1/2Bond-Alternating Spin Chain with a Next-Nearest-Neighbor Interaction in Magnetic Fields

Mamoru Usami, Sei-ichiro Suga

Published Oct 15, 2000• 1 citation
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Abstract

The dynamical structure factor of the S=1/2 bond-alternating spin chain with a next-nearest-neighbor interaction in magnetic field is investigated using the continued fraction method based on the Lanczos algorithm. When the plateau exists on the magnetization curve, the longitudinal dynamical structure factor shows a large intensity with a periodic dispersion relation, while the transverse one shows a large intensity with an almost dispersionless mode. The periodicity and the amplitude of the dispersion relation in the longitudinal dynamical structure factor are sensitive to the coupling constants. The dynamical structure factor of the S=1/2 two-leg ladder in magnetic field is also calculated in the strong interchain-coupling regime. The dynamical structure factor shows gapless or gapful behavior depending on the wave vector along the rung.

DOI
10.1143/jpsj.69.3419

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We calculate dynamical structure factors of the S=1S=1S=1 bond-alternating Heisenberg chain with a single-ion anisotropy in transverse magnetic fields, using a continued fraction method based on the Lanczos algorithm. In the Haldane-gap phase and the dimer phase, dynamical structure factors show characteristic field dependence. Possible interpretations are discussed in the viewpoint of the field dependence of the excitation continuum. The numerical results are in qualitative agreement with recent results for inelastic neutron-scattering experiments on the S=1S=1S=1 bond-alternating Heisenberg-chain compound Ni(C9D24N4)(NO2)ClO4\mathrm{Ni}({\mathrm{C}}_{9}{\mathrm{D}}_{24}{\mathrm{N}}_{4})(\mathrm{N}{\mathrm{O}}_{2})\mathrm{Cl}{\mathrm{O}}_{4}Ni(C9​D24​N4​)(NO2​)ClO4​ and the S=1S=1S=1 Haldane-gap compound Ni(C5D14N2)2N3(PF6)\mathrm{Ni}{({\mathrm{C}}_{5}{\mathrm{D}}_{14}{\mathrm{N}}_{2})}_{2}{\mathrm{N}}_{3}(\mathrm{P}{\mathrm{F}}_{6})Ni(C5​D14​N2​)2​N3​(PF6​) in transverse magnetic fields.