Integrable chain model with additional staggered model parameter

The generalization of the Yang-Baxter equations (YBE) in the presence of Z( 2) grading along both chain and time directions is presented. The XXZ model with staggered disposition along a chain of both, the anisotropy +/-Delta, as well as shifts of the spectral parameters are considered and the corres ponding integrable model is constructed. The Hamiltonian of the model is co mputed in fermionic and spin formulations. It involves three neighbour sire interactions and therefore can be considered as a zigzag ladder model. The algebraic Bethe ansatz technique is applied and the eigenstates, along wit h eigenvalues of the transfer matrix of the model are found. The model has a free fermionic limit at Delta = 0 and the integrable boundary terms are f ound in this case. This construction is quite general and can be applied to other known integr able models. (C) 2000 Elsevier Science B.V. All rights reserved.