EXACT EVALUATION OF THERMODYNAMIC QUANTITIES FOR THE INTEGRABLE T-J CHAIN

The supersymmetric tJ model in one dimension is investigated by means of the quantum transfer matrix (QTM). The free energy of the quantum s ystem is given by just the largest eigenvalue of the QTM whereas the n ext-largest ones determine the correlation lengths at finite temperatu re. The first step of the analysis consists of an embedding of the QTM into a family of commuting matrices. In the second step the eigenvalu e equations are derived by an algebraic Bethe ansatz. Finally, the eig envalue equations are transformed into a set of nonlinear integral equ ations. Some numerical results are presented. The specific heat for in stance shows the typical Luttinger liquid behavior at low temperatures .