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Propagating S=1/2 particles in S=1 Haldane gap systems

Karlo Penc, Hiroyuki Shiba

cond-matarXiv:cond-mat/9502085

Abstract

Inspired by the recent experiments on Y2-xCaxBaNiO5, (J. F. DiTusa et al., Phys. Rev. Lett. 73, 1857 (1994)), we discuss the dispersion relation of the s=1/2 particles in the s=1 Heisenberg and VBS model in the limit of small hopping amplitudes. The effective s=1/2 edge spins mix with the spin of the impurity resulting in one four--fold and two two--fold degenarate bands. We briefly discuss the interaction between the s=1/2 particles arising from the background.

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