Spectrum of the supersymmetric t-J model

The t-J model is soluble at the supersymmetric point J=-2t in one dimension using the Bethe ansatz (BA). The BA equations for finite chains are solved for the quasimomenta kj, which are needed to build the Bethe wave function. Bound states are found explicitly when pairs of the quasimomenta are complex. In the thermodynamic limit, they occur in string form. In this limit, elementary excitations above the ground state can be written in terms of so-called 'BA holes'. By considering certain excitations of the model, the holon and spinon dispersion curves are obtained for finite systems. Comparisons with exact diagonalisation are made to demonstrate the validity of the data. ((orig.))