FINITE-TEMPERATURE CORRELATION-FUNCTIONS OF THE HALDANE-SHASTRY MODEL

Using numerical diagonalization of small systems we obtain the thermod ynamics of the S = 1/2 and S = 1 Haldane-Shastry (HS) model. We study the correlation functions and the susceptibility and compare them with the results for the Heisenberg (H) model. We find evidence that in th e S = 1 case the low-T susceptibility decays exponentially to zero, in dicating the existence of a gap, in agreement with our earlier study o f the ground-state properties. The correlation functions (S-z(O)S-z(m) ) for the HS model decay faster than for the Heisenberg case, with bot h. m and temperature for both values of the spin. For large T all corr elation functions for the HS model become negative.