Bethe ansatz for the one-dimensional small-polaron model with open boundary conditions

The one-dimensional small-polaron model with open boundary conditions is considered in the framework of the quantum inverse scattering method. The spin model which is equivalent to the small-polaron model is the Heisenberg $XXZ$ spin chain in an external magnetic field. For spin model, the solutions of the reflection equation (RE) and the dual RE are obtained. The eigenvalues and eigenvectors problems are solved by using the algebraic Bethe ansatz method. The case of the fermion model is also studied, the commuting of the transfer matrix can be proved, and the eigenvalues and the Bethe ansatz equations for fermion model are obtained.