PERTURBATION-THEORY FOR THE TRIANGULAR HEISENBERG-ANTIFERROMAGNET WITH ISING-LIKE ANISOTROPY

It has been argued that the case of strong uniaxial anisotropy is especially favourable for the formation of a spin-liquid state in the S = 1/2 triangular Heisenberg antiferromagnet [77]. We reconsider the old arguments using up-to-date numerical techniques, and extend the study to general values of S. Recent progress in the understanding of this frustrated quantum spin system sheds light on the question why the original arguments in favour of an RVB state can not be conclusive. Our present results indicate that the tendency towards three-sublattice ordering is much stronger than it had been thought. However, the case S = 1/2 is still seen to be set apart from the cases S > 1/2, and for S = 1/2 the existence of true long-range order in the ground state remains debatable.