Topological quantum paramagnet in a quantum spin ladder
Topological quantum paramagnet in a quantum spin ladder
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量子自旋梯中的拓扑量子顺磁体
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
A. Schnyder
中科院分区：
文献类型：
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作者：
D. G. Joshi;A. Schnyder
最近发现，有序介质的玻色激发，如声子或自旋，可以表现出拓扑上的非平凡的能带结构。特别令人感兴趣的是量子磁铁中的磁振子和三重子激发，因为它们可以很容易地被外加磁场操纵。在这里，我们研究了S=1/2量子自旋阶梯中的三重子激发，表明它们表现出非平凡的拓扑，即使在量子无序顺磁相中也是如此。我们的分析表明，顺磁相实际上由两个不同的区域组成，它们在拓扑上具有不同的三重子激发。我们证明了这两个区域之间的拓扑转变可以通过外加磁场来调节。推导并计算了表征三元组拓扑结构的绕组数。通过体边界对应，我们发现非零缠绕数意味着局域三重子端态的存在。讨论了拓扑顺磁相的实验特征和可能的物理实现。
It has recently been found that bosonic excitations of ordered media, such as phonons or spinons, can exhibit topologically nontrivial band structures. Of particular interest are magnon and triplon excitations in quantum magnets, as they can easily be manipulated by an applied field. Here we study triplon excitations in an S=1/2 quantum spin ladder and show that they exhibit nontrivial topology, even in the quantum-disordered paramagnetic phase. Our analysis reveals that the paramagnetic phase actually consists of two separate regions with topologically distinct triplon excitations. We demonstrate that the topological transition between these two regions can be tuned by an external magnetic field. The winding number that characterizes the topology of the triplons is derived and evaluated. By the bulk-boundary correspondence, we find that the non-zero winding number implies the presence of localized triplon end states. Experimental signatures and possible physical realizations of the topological paramagnetic phase are discussed.