Semiclassical theory of the magnetization process of the triangular lattice Heisenberg model
Semiclassical theory of the magnetization process of the triangular lattice Heisenberg model
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DOI：
10.1103/physrevb.94.075136
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发表时间：
2016-08-17
影响因子：
3.7
通讯作者：
Mila, Frederic
中科院分区：
文献类型：
--
作者：
Coletta, Tommaso;Toth, Tamas A.;Mila, Frederic
受自旋范围为 1/2 至 5/2 的三角晶格海森堡反铁磁体中 1/3 磁化平台的众多示例的启发，我们重新审视该模型磁化曲线的半经典计算，目的是提出一种简单的方法，使人们能够计算完整的磁化曲线，而不仅仅是 1/3 平台的临界场。我们表明，实际上可以完全在线性自旋波理论中计算磁化曲线，包括第一次量子校正和 1/3 平台的出现，并且对临界场的预测与很久以前基于需要超越线性自旋波理论的论证得出的结果一致，符合 1/S 阶。该计算依赖于中心观察，即在经典基态是共线的上下结构的场中，半经典能量存在扭结，并且当所有场的所有半经典基态相互比较时，这种扭结会导致能量与场的局部线性行为。以这种方式计算出的自旋 1/2、1 和 5/2 的磁化曲线与现有的实验数据非常吻合。
Motivated by the numerous examples of 1/3 magnetization plateaux in the triangular-lattice Heisenberg antiferromagnet with spins ranging from 1/2 to 5/2, we revisit the semiclassical calculation of the magnetization curve of that model, with the aim of coming up with a simple method that allows one to calculate the full magnetization curve and not just the critical fields of the 1/3 plateau. We show that it is actually possible to calculate the magnetization curve including the first quantum corrections and the appearance of the 1/3 plateau entirely within linear spin-wave theory, with predictions for the critical fields that agree to order 1/S with those derived a long time ago on the basis of arguments that required going beyond linear spin-wave theory. This calculation relies on the central observation that there is a kink in the semiclassical energy at the field where the classical ground state is the collinear up-up-down structure and that this kink gives rise to a locally linear behavior of the energy with the field when all semiclassical ground states are compared to each other for all fields. The magnetization curves calculated in this way for spin 1/2, 1, and 5/2 are shown to be in good agreement with available experimental data.