Quantum fluctuations in anisotropic triangular lattices with ferromagnetic and antiferromagnetic exchange
Quantum fluctuations in anisotropic triangular lattices with ferromagnetic and antiferromagnetic exchange
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DOI：
10.1103/physrevb.89.184402
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发表时间：
2014-04
影响因子：
3.7
通讯作者：
B. Schmidt;P. Thalmeier
中科院分区：
文献类型：
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作者：
B. Schmidt;P. Thalmeier
三角形晶格上的海森堡模型是几何受挫自旋系统的一个典型例子。然而，大多数实验上可获得的化合物具有空间各向异性的交换相互作用。作为该各向异性的函数，可以实现具有不同磁性的基态。受最近在${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4\ensuremath{-}x}{\mathrm{Br}}_{x}$，上的实验结果的启发，我们讨论了具有两个交换常数${J}_{1}$和${J}_{2}$的各向异性模型的完整相图，包括可能的铁磁交换。并与相关的正方形晶格模型进行了比较。我们在经典能级上讨论了零温相图、有序向量、基态能量和有序矩，并在自旋波理论的框架下研究了量子涨落的影响。结果表明，有序矩的场依赖于场和控制参数是非单调的。
The Heisenberg model on a triangular lattice is a prime example of a geometrically frustrated spin system. However most experimentally accessible compounds have spatially anisotropic exchange interactions. As a function of this anisotropy, ground states with different magnetic properties can be realized. Motivated by recent experimental findings on ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4\ensuremath{-}x}{\mathrm{Br}}_{x}$, we discuss the full phase diagram of the anisotropic model with two exchange constants ${J}_{1}$ and ${J}_{2}$, including possible ferromagnetic exchange. Furthermore a comparison with the related square lattice model is carried out. We discuss the zero-temperature phase diagram, ordering vector, ground-state energy, and ordered moment on a classical level and investigate the effect of quantum fluctuations within the framework of spin-wave theory. The field dependence of the ordered moment is shown to be nonmonotonic with field and control parameter.