Exact solution of XXZ spin chain with unparallel boundary fields

By using a set of gauge transformations (face-vertex correspondence relations), the XXZ spin chain with both transverse and longitudinal magnetic boundary fields is studied. The corresponding reflection boundary matrices therefore have non-diagonal elements. The Bethe ansatz equations, the eigenvalues and the eigenstates of the transfer matrix and the Hamiltonian of the system are obtained in the framework of algebraic Bethe ansatz method. The ground states for different couplings are derived. (C) 2003 Elsevier B.V. All rights reserved.