Spinons and triplons in spatially anisotropic frustrated antiferromagnets
Spinons and triplons in spatially anisotropic frustrated antiferromagnets
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DOI：
10.1038/nphys749
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发表时间：
2007-11-01
期刊：
影响因子：
19.6
通讯作者：
Balents, Leon
中科院分区：
文献类型：
--
作者：
Kohno, Masanori;Starykh, Oleg A.;Balents, Leon
寻找分数量子数的基本激发是现代凝聚态物理学的核心挑战。长期以来，人们一直猜测，二维受挫磁体可能支持具有中性自旋1/2激发的量子无序状态，即所谓的自旋。然而，尽管进行了几十年的研究，也没有发现明确的实验例子。我们使用一个真实的模型探索了几种材料的可能性，在二维中，自旋1/2空间各向异性受挫的海森堡反铁磁体。在这里，我们推导出一个有效的薛定谔方程适用于弱链间耦合区域。用这种方法得到的动力学自旋关联在没有参数拟合的情况下与三角反铁磁体Cs2CuCl4的非弹性中子测量结果是定量一致的。在这种反铁磁体中，光谱由由单链的一维自旋效应引起的非相干连续体和由于两个自旋的三重子束缚态的相干传播而产生的尖锐的色散峰组成。我们认为，三子是空间各向异性受挫反铁磁体的一般特征，这是由于束缚自旋对通过链之间的传播降低了它的动能而产生的。
The search for elementary excitations with fractional quantum numbers is a central challenge in modern condensed-matter physics. It has long been speculated that two-dimensional frustrated magnets might support quantum disordered states with neutral spin-1/2 excitations known as spinons. Despite decades of search, however, no clear experimental examples have been found. We explore the possibility for several materials using a realistic model, the spin-1/2 spatially anisotropic frustrated Heisenberg antiferromagnet in two dimensions. Here, we derive an effective Schrodinger equation valid in the weak interchain coupling regime. The dynamical spin correlations from this approach agree quantitatively without fitting parameters with inelastic neutron measurements of the triangular antiferromagnet Cs2CuCl4. In such antiferromagnets, the spectrum is composed of an incoherent continuum arising from the effects of one-dimensional spinons of individual chains, and a sharp dispersing peak, due to coherently propagating 'triplon' bound states of two spinons. We argue that triplons are generic features of spatially anisotropic frustrated antiferromagnets, which arise because the bound spinon pair lowers its kinetic energy by propagating between chains.