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Double gap and solitonic excitations in the spin-Peierls chain CuGeO3

M. Ain·J. E. Lorenzo·L. P. Regnault·G. Dhalenne·A. Revcolevschi·B. Hennion·Th. Jolicoeur
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Abstract

We have studied magnetic excitations in the dimerized spin-Peierls phase of CuGeO3, by high resolution inelastic neutron scattering. We measured the well-defined spin triplet dispersive mode which is gapped throughout the whole Brillouin zone. We also observed that this mode is separated by an unexpected second gap of order 2 meV from a continuum of magnetic excitations extending to higher energy. The first gap (or 'triplet gap') and its associated dispersive mode is due to the breaking of a singlet dimer into a delocalized triplet. We propose that the second gap (or 'solitonic gap') and the continuum correspond to dissociation of that triplet into two unbound spin-1/2 solitons that are separated by a dimerized region of arbitrary length.

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M. Ain, J. E. Lorenzo, L. P. Regnault, G. Dhalenne, A. Revcolevschi, B. Hennion, Th. Jolicoeur. 1998-02-09. Double gap and solitonic excitations in the spin-Peierls chain CuGeO3. https://doi.org/10.1103/physrevlett.78.1560

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