Integrability and exact solution for coupled BCS systems associated with   the $su(4)$ Lie algebra
  We introduce an integrable model for two coupled BCS systems through a solution of the Yang-Baxter equation associated with the Lie algebra $su(4)$. By employing the algebraic Bethe ansatz, we determine the exact solution for the energy spectrum. An asymptotic analysis is conducted to determine the leading terms in the ground state energy, the gap and some one point correlation functions at zero temperature. 
Xi-Wen Guan, Angela Foerster, Jon Links and Huan-Qiang Zhou