Pd. Sacramento et Vr. Vieira, FINITE-TEMPERATURE CORRELATION-FUNCTIONS OF THE HALDANE-SHASTRY MODEL, Journal of physics. Condensed matter, 7(45), 1995, pp. 8619-8628
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.