Elementary Excitations of Heisenberg Ferrimagnetic Spin Chains
Abstract
We numerically investigate elementary excitations of the Heisenberg alternating-spin chains with two kinds of spins 1 and 1/2 antiferromagnetically coupled to each other. Employing a recently developed efficient Monte Carlo technique as well as an exact diagonalization method, we verify the spin-wave argument that the model exhibits two distinct excitations from the ground state which are gapless and gapped. The gapless branch shows a quadratic dispersion in the small-momentum region, which is of ferromagnetic type. With the intention of elucidating the physical mechanism of both excitations, we make a perturbation approach from the decoupled-dimer limit. The gapless branch is directly related to spin 1's, while the gapped branch originates from cooperation of the two kinds of spins.
Keywords
Cite
@article{arxiv.cond-mat/9710332,
title = {Elementary Excitations of Heisenberg Ferrimagnetic Spin Chains},
author = {Shoji Yamamoto and S. Brehmer and H. -J. Mikeska},
journal= {arXiv preprint arXiv:cond-mat/9710332},
year = {2009}
}
Comments
7 pages, 7 Postscript figures, RevTex