Integrable models for Bose–Einstein condensates in a double-well potential formulated from Holstein–Primakoff transformations

We present three families of integrable models for Bose–Einstein condensates in a double-well potential which are based on the combination, two by two, of three algebraic realizations of the Lax operator: the bosonic realization and the su(2) and su(1, 1) Holstein–Primakoff realizations. The families of Hamiltonians describe Josephson tunneling between two condensates in a double-well potential with boson distribution dependence in the tunneling term. Two families describe models with interacting bosons and the other does not. The integrability is shown by using the quantum inverse scattering method and algebraic Bethe ansatz. The energy eigenvalues and the Bethe ansatz equations are obtained for each model proposed. In the end, we use the energy gap as a testing function to compare the proposed integrable models with the well-known integrable two-site Bose–Hubbard model to show the effect of the boson distribution in the tunneling. (paper)