T-W relation and free energy of the antiperiodic XXZ chain with η=iπ/3 at a finite temperature

We study the thermodynamics of the antiperiodic XXZ chain with anisotropy parameter η=iπ/3 by means of the t-W method. We parameterize the eigenvalues of both the transfer matrix and the corresponding fused transfer matrix by their zero points instead of Bethe roots. Based on the patterns of the zero points distribution and the reconstructed entropy, we obtain the nonlinear integral equations (NLIEs) describing the thermodynamics of the model and compute its free energy at a finite temperature.