Structure of the magnetic excitations in the spin-1/2 triangular-lattice Heisenberg antiferromagnet Ba(3)CoSb(2)O(9).
Structure of the magnetic excitations in the spin-1/2 triangular-lattice Heisenberg antiferromagnet Ba(3)CoSb(2)O(9).
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DOI：
10.1038/s41467-017-00316-x
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发表时间：
2017-08-10
影响因子：
16.6
通讯作者：
Kakurai K
中科院分区：
文献类型：
--
作者：
Ito S;Kurita N;Tanaka H;Ohira-Kawamura S;Nakajima K;Itoh S;Kuwahara K;Kakurai K
自旋为1/2的三角格子海森堡反铁磁体（TLHAF）是一种典型的受抑量子磁体，它表现出显著的量子多体效应，这种效应是由自旋受抑和量子涨落的协同作用引起的.自旋为1/2的TLHAF的基态性质在理论上是很好理解的。然而，关于磁激发的理论共识是有限的。自旋为1/2的TLHAF中磁激发的实验研究也很有限。在这里，我们显示的结构的磁激发自旋1/2 TLHAF Ba 3CoSb 2 O 9的非弹性中子散射研究。与理论预期明显不同的是，激发光谱具有三级能量结构。最低能量的第一阶段由单磁振子激发的色散分支组成。第二和第三阶段是色散连续伴随着一个柱状连续延伸超过10 meV，这是6倍大于交换相互作用J = 1.67 meV。我们的研究结果表明，目前的理论框架的缺点。二维受抑磁体被大量研究，因为理论预测量子效应可能导致出现分数激发。Ito等人使用非弹性中子散射表明Ba 3CoSb 2 O 9的激发光谱与当前的理论预期不一致。
A spin-1/2 triangular-lattice Heisenberg antiferromagnet (TLHAF) is a prototypical frustrated quantum magnet, which exhibits remarkable quantum many-body effects that arise from the synergy between spin frustration and quantum fluctuation. The ground-state properties of a spin-1/2 TLHAF are theoretically well understood. However, the theoretical consensus regarding the magnetic excitations is limited. The experimental study of the magnetic excitations in spin-1/2 TLHAFs has also been limited. Here we show the structure of magnetic excitations in the spin-1/2 TLHAF Ba3CoSb2O9 investigated by inelastic neutron scattering. Significantly different from theoretical expectations, the excitation spectrum has a three-stage energy structure. The lowest-energy first stage is composed of dispersion branches of single-magnon excitations. The second and third stages are dispersive continua accompanied by a columnar continuum extending above 10 meV, which is six times larger than the exchange interaction J = 1.67 meV. Our results indicate the shortcomings of the current theoretical framework. Two-dimensional frustrated magnets are heavily studied because theories predict that quantum effects may lead to the emergence of fractionalized excitations. Ito et al. use inelastic neutron scattering to show that the excitation spectrum of Ba3CoSb2O9 disagrees with current theoretical expectations.
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