Ramos E, Franco R, Silva-Valencia J, Foglio M E, Figueira M S
Departamento de Física, Universidad Nacional de Colombia, A. A. 5997, Bogotá, Colombia.
J Phys Condens Matter. 2017 Aug 31;29(34):345601. doi: 10.1088/1361-648X/aa791b. Epub 2017 Jun 13.
In this article we investigate the effects of short-range anti-ferromagnetic correlations on the gap opening of topological Kondo insulators. We add a Heisenberg term to the periodic Anderson model at the limit of strong correlations in order to allow a small degree of hopping of the localized electrons between neighboring sites of the lattice. This new model is adequate for studying topological Kondo insulators, whose paradigmatic material is the compound [Formula: see text]. The main finding of the article is that the short-range antiferromagnetic correlations, present in some Kondo insulators, contribute decisively to the opening of the Kondo gap in their density of states. These correlations are produced by the interaction between moments on the neighboring sites of the lattice. For simplicity, we solve the problem on a two dimensional square lattice. The starting point of the model is the [Formula: see text] ions orbitals, with [Formula: see text] multiplet in the presence of spin-orbit coupling. We present results for the Kondo and for the antiferromagnetic correlation functions. We calculate the phase diagram of the model, and as we vary the [Formula: see text] level position from the empty regime to the Kondo regime, the system develops metallic and topological Kondo insulator phases. The band structure calculated shows that the model describes a strong topological insulator.
在本文中，我们研究了短程反铁磁关联对拓扑近藤绝缘体能隙打开的影响。我们在强关联极限下向周期安德森模型中添加一个海森堡项，以便使局域电子在晶格的相邻格点之间有小程度的跳跃。这个新模型适用于研究拓扑近藤绝缘体，其典型材料是化合物[公式：见原文]。本文的主要发现是，一些近藤绝缘体中存在的短程反铁磁关联对其态密度中近藤能隙的打开起决定性作用。这些关联是由晶格相邻格点上的磁矩之间的相互作用产生的。为简单起见，我们在二维正方晶格上求解该问题。模型的起点是[公式：见原文]离子轨道，在自旋轨道耦合存在下具有[公式：见原文]多重态。我们给出了近藤和反铁磁关联函数的结果。我们计算了模型的相图，并且当我们将[公式：见原文]能级位置从空穴区变化到近藤区时，系统会发展出金属相和拓扑近藤绝缘相。计算得到的能带结构表明该模型描述的是一种强拓扑绝缘体。
