We consider a one-dimensional two-band model of electrons on a lattice with nearest-neighbor hopping t constrained by the excluded multiple occupancy of the sites, an interband splitting, Δ, and intraband and interband exchange J between neighboring sites. This model is integrable at the supersymmetric point and reduces to the SU(4)-invariant supersymmetric t-J model with crystal field splitting. We present the exact solution via Bethe’s ansatz and discuss ground-state properties and the excitation spectrum as a function of Δ.

• Received 6 July 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.2396