2006/07/07 by Doron L. Bergman, Ryuichi Shindou, Gregory A. Fiete +1 · 4 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.75.094403
published as Phys. Rev. B 75, 094403 (2007) (31 pages)
arxiv created 2006/07/07 · openalex publication_date 2007/03/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study the effect of quantum fluctuations on the half-polarized magnetization plateau of a pyrochlore antiferromagnet. We argue that an expansion around the easy-axis limit is appropriate for discussing the ground-state selection among the classically degenerate manifold of collinear states with a 3:1 ratio of spins parallel and/or antiparallel to the magnetization axis. A general approach to the necessary degenerate perturbation theory is presented, and an effective quantum dimer model within this degenerate manifold is derived for arbitrary spin s. We also generalize the existing semiclassical analysis of Hizi and Henley [Phys. Rev. B 73, 054403 (2006)] to the easy-axis limit and show that both approaches agree at large s. We show that under rather general conditions, the first nonconstant terms in the effective Hamiltonian for s\ensuremath\geqslant1 occur only at sixth order in the transverse exchange coupling. For s\ensuremath\geqslant5∕2, the dominant terms in the effective Hamiltonian are those of a classical dimer model, which predicts a magnetically ordered state. For s\ensuremath\leqslant2, more exotic possibilities may be realized. The effective dimer Hamiltonian is then strongly quantum. We describe two likely ground states in that regime.