Static and Dynamical Properties of the Spin-1/2 Equilateral Triangular-Lattice Antiferromagnet Ba3CoSb2O9
Static and Dynamical Properties of the Spin-1/2 Equilateral Triangular-Lattice Antiferromagnet Ba3CoSb2O9
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DOI：
10.1103/physrevlett.116.087201
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发表时间：
2016-02-24
影响因子：
8.6
通讯作者：
Matsuda, M.
中科院分区：
文献类型：
--
作者：
Ma, J.;Kamiya, Y.;Matsuda, M.
我们提出了自旋 1/2 等边三角晶格反铁磁体 Ba3CoSb2O9 的单晶中子散射测量。除了确认零磁场下 Co2+ 磁矩位于 ab 平面，然后确定最小准二维自旋哈密顿量的所有交换参数之外，我们还通过观察本征线展宽提供了磁振子衰变的结论性实验证据。通过与线性和非线性自旋波理论的详细比较，我们还指出，传统上用于预测非共线磁体磁振子衰变的大S近似不足以解释我们的实验观察结果。因此，我们的结果需要一个新的理论框架来描述强量子效应下低维受挫磁体的激发光谱。
We present single-crystal neutron scattering measurements of the spin-1/2 equilateral triangular-lattice antiferromagnet Ba3CoSb2O9. Besides confirming that the Co2+ magnetic moments lie in the ab plane for zero magnetic field and then determining all the exchange parameters of the minimal quasi-2D spin Hamiltonian, we provide conclusive experimental evidence of magnon decay through observation of intrinsic line broadening. Through detailed comparisons with the linear and nonlinear spin-wave theories, we also point out that the large-S approximation, which is conventionally employed to predict magnon decay in noncollinear magnets, is inadequate to explain our experimental observation. Thus, our results call for a new theoretical framework for describing excitation spectra in low-dimensional frustrated magnets under strong quantum effects.