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Excitation Spectra of Structurally Dimerized and Spin-Peierls Chains in a Magnetic Field

Weiqiang Yu·Stephan Haas
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Abstract

The dynamical spin structure factor and the Raman response are calculated for structurally dimerized and spin-Peierls chains in a magnetic field, using exact diagonalization techniques. In both cases there is a spin liquid phase composed of interacting singlet dimers at small fields h < h_c1, an incommensurate regime (h_c1 < h < h_c2) in which the modulation of the triplet excitation spectra adapts to the applied field, and a fully spin polarized phase above an upper critical field h_c2. For structurally dimerized chains, the spin gap closes in the incommensurate phase, whereas spin-Peierls chains remain gapped. In the spin liquid regimes, the dominant feature of the triplet spectra is a one-magnon bound state, separated from a continuum of states at higher energies. There are also indications of a singlet bound state above the one-magnon triplet.

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Weiqiang Yu, Stephan Haas. 1999-09-06. Excitation Spectra of Structurally Dimerized and Spin-Peierls Chains in a Magnetic Field. https://doi.org/10.1103/physrevb.62.344

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