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Phys. Rev. Lett. 80, 2709–2712 (1998)

Non-Haldane Spin-Liquid Models with Exact Ground States

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A. K. Kolezhuk*
Institut für Theoretische Physik, Universität Hannover, Appelstrasse 2, 30167 Hannover, Germany,
and Institute of Magnetism, National Academy of Sciences and Ministry of Education of Ukraine, 252142 Kiev, Ukraine

H.-J. Mikeska
Institut für Theoretische Physik, Universität Hannover, Appelstrasse 2, 30167 Hannover, Germany

Received 8 December 1997; published in the issue dated 23 March 1998

We present a family of spin-ladder models which can be solved exactly for the ground state and exhibit non-Haldane spin-liquid properties as predicted recently by Nersesyan and Tsvelik [Phys. Rev. Lett. 78, 3939 (1997)], and study their excitation spectra using a simple variational Ansatz. The elementary excitation is neither a magnon nor a spinon, but a pair of propagating triplet or singlet solitons connecting two spontaneously dimerized ground states. Second-order phase transitions separate this phase from the Haldane phase and the rung-dimer phase.

© 1998 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.80.2709
DOI:
10.1103/PhysRevLett.80.2709
PACS:
75.10.Jm, 75.40.Cx, 75.40.Gb

*Permanent address: Institute of Magnetism, 36(b) Vernadskii avenue, 252142 Kiev, Ukraine.

 
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