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We study with exact diagonalization techniques the Heisenberg model for a system of SU (2) spins with S=1/2 and random infinite-range exchange interactions. We calculate the critical temperature T₆ for the spin-glass to paramagnetic transition. We obtain T₆0. 13, in good agreement with previous quantum Monte Carlo and analytical estimates. We provide a detailed picture for the different kind of excitations which intervene in the dynamical response ^'' (, T) at T=0 and analyze their evolution as T increases. We also calculate the specific heat Cₕ (T). We find that it displays a smooth maximum at T₌0. 25, in good qualitative agreement with experiments. We argue that the fact that T₌>T₆ is due to a quantum disorder effect.
Arrachea et al. (Thu,) studied this question.