Order versus disorder in the quantum Heisenberg antiferromagnet on the kagomé lattice using exact spectra analysis

作者：P. Lecheminant, B. Bernu, C. Lhuillier, Laurent Pierre, Philippe Sindzingre · 发表于：Physical review. B, Condensed matter · 年份：1997 · DOI：10.1103/physrevb.56.2521 · 被引用次数：364 · 研究领域：Advanced Condensed Matter Physics、Physics of Superconductivity and Magnetism、Theoretical and Computational Physics

A group-symmetry analysis of the low-lying levels of the spin-1/2 kagom\'e Heisenberg antiferromagnet is performed for small samples up to $N=27$. This approach allows one to follow the effect of quantum fluctuations when the sample size increases. The results contradict the scenario of ``order by disorder'' which has been advanced on the basis of large-$S$ calculations. A large enough second-neighbor ferromagnetic exchange coupling is needed to stabilize the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ pattern: the finite-size analysis indicates a quantum critical transition at a nonzero coupling.