Kondo route to spin inhomogeneities in the honeycomb Kitaev model
Kondo route to spin inhomogeneities in the honeycomb Kitaev model
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DOI：
10.1103/physrevb.94.024411
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发表时间：
2015-09
影响因子：
3.7
通讯作者：
S. Das;K. Dhochak;V. Tripathi
中科院分区：
文献类型：
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作者：
S. Das;K. Dhochak;V. Tripathi
量子自旋液体中的顺磁杂质可以导致具有非常不寻常性质的近藤效应。本文研究了顺磁性杂质与自旋为1/2的蜂窝Kitaev模型在无带隙自旋液相中的局域交换耦合效应。的（杂质）标度方程被发现是不敏感的符号的耦合。弱耦合和强耦合不动点是稳定的，后者分别对应于反铁磁和铁磁情况下的非相互作用的空位和相互作用的自旋1缺陷。在这两种情况下，在强耦合极限的基态具有一个非平凡的拓扑结构与一个有限的Z2通量在杂质网站。对于反铁磁情况，由于Kitaev模型的可积性，可以直接得到这个结果。然而，强耦合的铁磁情况下的限制是不可积的，我们解决这个问题，通过精确的对角化计算有限Kitaev片段。我们的精确对角化计算表明，从弱到强的耦合相变和拓扑相变发生得相当接近，并且可能是一致的。我们还发现了一个有趣的相似性之间的磁响应的缺陷和杂质的磁化率在双通道近藤问题。
Paramagnetic impurities in a quantum spin-liquid can result in Kondo effects with highly unusual properties. We have studied the effect of locally exchange-coupling a paramagnetic impurity with the spin-1/2 honeycomb Kitaev model in its gapless spin-liquid phase. The (impurity) scaling equations are found to be insensitive to the sign of the coupling. The weak and strong coupling fixed points are stable, with the latter corresponding to a noninteracting vacancy and an interacting, spin-1 defect for the antiferromagnetic and ferromagnetic cases respectively. The ground state in the strong coupling limit in both cases has a nontrivial topology associated with a finite Z2 flux at the impurity site. For the antiferromagnetic case, this result can be obtained straightforwardly owing to the integrability of the Kitaev model with a vacancy. The strong-coupling limit of the ferromagnetic case is however nonintegrable, and we address this problem through exact-diagonalization calculations with finite Kitaev fragments. Our exact diagonalization calculations indicate that that the weak to strong coupling transition and the topological phase transition occur rather close to each other and are possibly coincident. We also find an intriguing similarity between the magnetic response of the defect and the impurity susceptibility in the two-channel Kondo problem.