Europhys. Lett, 47 (3), pp. 364-370 (1999)
An exactly solvable model of generalized spin ladder
S. Albeverio 1, S.-M. Fei 1 and Y. Wang 2
1 Institut für Angewandte Mathematik,
Universität Bonn - D-53115 Bonn, Germany
Fakultät für Mathematik, Ruhr-Universität Bochum - D-4478 Bochum, Germany
2 Institut für Physik, Universität Augsburg - 86135 Augsburg, Germany
Laboratory of Ultra-Low Temperature Physics, Chinese Academy of Science
Beijing 100080, PRC
(received 11 February 1999; accepted in final form 1 June 1999)
PACS. 75.10Jm - Quantized spin models.
A detailed study of an spin ladder model is given. The ladder consists of plaquettes formed by nearest-neighbor rungs with all possible SU(2)-invariant interactions. For properly chosen coupling constants, the model is shown to be integrable in the sense that the quantum Yang-Baxter equation holds and one has an infinite number of conserved quantities. The R-matrix and L-operator associated with the model Hamiltonian are given in a limiting case. It is shown that after a simple transformation, the model can be solved via a Bethe ansatz. The phase diagram of the ground state is exactly derived using the Bethe ansatz equation.
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