2005/02/28 by Jean-Christophe Domenge, Philippe Sindzingre, Claire Lhuillier +3 · 1 citation
Physics and Astronomy · #Advanced Condensed Matter Physics #Cold Atom Physics and Bose-Einstein Condensates #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.72.024433
published as Phys. Rev. B 72, 024433 (2005) · Accepted for publication in Phys. Rev. B (2005)
arxiv created 2005/07/05 · openalex publication_date 2005/07/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Motivated by recent experiments on an S=1∕2 antiferromagnet on the kagom'e lattice, we investigate the Heisenberg J1\ensuremath-J2 model with ferromagnetic J1 and antiferromagnetic J2, Classically the ground state displays N'eel long-range order with 12 noncoplanar sublattices. The order parameter has the symmetry of a cuboctahedron, it fully breaks SO(3) as well as the spin-flip symmetry, and we expect from the latter a ℤ2 symmetry breaking pattern. As might be expected from the Mermin-Wagner theorem in two dimensions, the SO(3) symmetry is restored by thermal fluctuations while the ℤ2 symmetry breaking persists up to a finite temperature. A complete study of S=1∕2 exact spectra reveals that the classical order subsists for quantum spins in a finite range of parameters. First-order spin wave calculations give the range of existence of this phase and the renormalizations at T=0 of the order parameters associated to both symmetry breakings. This phase is destroyed by quantum fluctuations for a small but finite J2∕\ensuremath|J1\ensuremath|\ensuremath≃3, consistently with exact spectra studies, which indicate a gapped phase.