Bethe states of the XXZ spin-1/2 chain with arbitrary boundary fields
  Based on the inhomogeneous T-Q relation constructed via the off-diagonal Bethe Ansatz, the Bethe-type eigenstates of the XXZ spin-1/2 chain with arbitrary boundary fields are constructed. It is found that by employing two sets of gauge transformations, proper generators and reference state for constructing Bethe vectors can be obtained respectively. Given an inhomogeneous T-Q relation for an eigenvalue, it is proven that the resulting Bethe state is an eigenstate of the transfer matrix, provided that the parameters of the generators satisfy the associated Bethe Ansatz equations. 
Xin Zhang, Yuan-Yuan Li, Junpeng Cao, Wen-Li Yang, Kangjie Shi and   Yupeng Wang
math-ph cond-mat.stat-mech hep-th math.MP