Two-temperature scales in the triangular-lattice Heisenberg antiferromagnet
Two-temperature scales in the triangular-lattice Heisenberg antiferromagnet
复制标题
三角晶格海森堡反铁磁体中的两个温标
DOI：
10.1103/physrevb.99.140404
复制
发表时间：
2019-04-10
影响因子：
3.7
通讯作者：
Li, Wei
中科院分区：
文献类型：
--
作者：
Chen, Lei;Qu, Dai-Wei;Li, Wei
范型阻挫自旋1/2三角格子海森堡反铁磁体（TLH）的反常热力学性质在实验和理论上都是一个开放的研究课题。在这里，我们进一步的理论理解的基础上，最近开发的，强大的指数张量重整化群方法在准一维（1D）设置的圆柱体和条纹，以及直接在2D的张量积算子的方法。所观察到的TLH的热性能与最近的两个实验测量的几乎理想的TLH材料Ba 8 CoNb 6 O24非常一致。值得注意的是，我们的数值模拟揭示了两个交叉温度标度，在T-l/J类似于0.20和T-h/J类似于0.55，与J海森堡交换耦合，这也证实了更仔细的检查实验数据。我们建议，在低温标度T-1和较高的一个T-h之间的中间制度，“rotonlike”激发被激活与一个强大的手征组分和热熵的贡献大。轴承显着相似的著名的roton热力学在液氦，这些缺口激发抑制了初期的120度秩序出现的温度低于T-I。
The anomalous thermodynamic properties of the paradigmatic frustrated spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLH) has remained an open topic of research over decades, both experimentally and theoretically. Here, we further the theoretical understanding based on the recently developed, powerful exponential tensor renormalization group method on cylinders and stripes in a quasi-one-dimensional (1D) setup, as well as a tensor product operator approach directly in 2D. The observed thermal properties of the TLH are in excellent agreement with two recent experimental measurements on the virtually ideal TLH material Ba8CoNb6O24. Remarkably, our numerical simulations reveal two crossover temperature scales, at T-l/J similar to 0.20 and T-h/J similar to 0.55, with J the Heisenberg exchange coupling, which are also confirmed by a more careful inspection of the experimental data. We propose that in the intermediate regime between the low-temperature scale T-l and the higher one T-h, the "rotonlike" excitations are activated with a strong chiral component and a large contribution to thermal entropies. Bearing remarkable resemblance to the renowned roton thermodynamics in liquid helium, these gapped excitations suppress the incipient 120 degrees order that emerges for temperatures below T-l.