Claire L'Huillier, (Univ P & M Curie), RVB States and Spin Liquids in 2D

Aug 16, 1999 RVB States and Spin Liquids in 2D Claire L'Huillier, (Univ P & M Curie) We display some characteristics of two distinct 2-dimensionnal "Quantum Disordered phases" recently studied in Paris VI and Hannover. The results have been obtained from a detailed analysis of finite size spectra ( exact diagonalisations with sample sizes up to 36). In these two models the spin 1/2 interact through SU(2) invariant hamiltonians and the lattices are "frustrating " (triangular based lattices). The Multi-Spin -Exchange hamiltonian exhibits various phase transitions from ferromagnetism to three subblattice long range order. For a very large window of coupling parameters it exhibits a "Spin Liquid Phase" with a large gap and short range correlations. The ground-state is unique (up to a topological degeneracy) . A singlet bound state might be present just below the first magnetic excitations. The second example is much more intriguing: the spin 1/2 Heisenberg hamiltonian on the kagome lattice has presumably gapless SINGLET excitations that cannot be reduced to a "single mode picture". The spin 1/2 excitations of this model may be deconfined and T-symmetry breaking.
cond-mat/9812329, cond-mat/9802168, cond-mat/9907220

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