On integrable directed polymer models on the square lattice

In a recent work Povolotsky (2013 J. Phys. A: Math. Theor. 46 465205) provided a three-parameter family of stochastic particle systems with zero-range interactions in one-dimension which are integrable by coordinate Bethe ansatz. Using these results we obtain the corresponding condition for integrability of a class of directed polymer models with random weights on the square lattice. Analyzing the solutions we find, besides known cases, a new two-parameter family of integrable DP model, which we call the Inverse-Beta polymer, and provide its Bethe ansatz solution.