paper

A frustrated spin-1 -- Heisenberg antiferromagnet: An anisotropic planar pyrochlore model

arXiv:1312.2420 · doi:10.1088/1742-6596/529/1/012008

Abstract

The zero-temperature ground-state (GS) properties and phase diagram of a frustrated spin-1 -- Heisenberg model on the checkerboard square lattice are studied, using the coupled cluster method. We consider the case where the nearest-neighbour exchange bonds have strength and the next-nearest-neighbour exchange bonds present (viz., in the checkerboard pattern of the planar pyrochlore) have strength . We find significant differences from both the spin-1/2 and classical versions of the model. We find that the spin-1 model has a first phase transition at (as does the classical model at ) between two antiferromagnetic phases, viz., a quasiclassical Néel phase (for ) and one of the infinitely degenerate family of quasiclassical phases (for ) that exists in the classical model for , which is now chosen by the {\it order by disorder} mechanism as (probably) the "doubled Néel" (or Néel) state. By contrast, none of this family survives quantum fluctuations to form a stable GS phase in the spin-1/2 case. We also find evidence for a second quantum critical point at in the spin-1 model, such that for the quasiclassical (Néel) ordering melts and a nonclassical phase appears, which, on the basis of preliminary evidence, appears unlikely to have crossed-dimer valence-bond crystalline (CDVBC) ordering, as in the spin-1/2 case. Unlike in the spin-1/2 case, where the Néel and CDVBC phases are separated by a phase with plaquette valence-bond crystalline (PVBC) ordering, we find very preliminary evidence for such a PVBC state in the spin-1 model for all .

References in corpus (25)

Cited by in corpus (1)