用Gutzwiller近似比较研究BaFe_2As_2和BaMn_2As_2的电磁性质
A comparative study of the electronic and magnetic properties of BaFe_2As_2 and BaMn_2As_2 using the Gutzwiller approximation
摘要：
为了阐明过渡金属离子在磷属元素化物材料中所起的作用，我们比较了BaFe_{2} As_{2}和BaMn_{2} As_{2}的电子和磁性。为此，我们采用LDA+Gutzwiller方法来分析这两个系统的质量重整化和有序磁矩的大小。我们研究了一个模型，包含所有五个过渡金属3d轨道连同Ba-5d和As-4p状态（ddp模型），并比较这些结果与向下折叠模型，由Fe/Mn d-状态（d模型）。电子关联处理使用多带Gutzwiller近似。用LDA+Gutzwiller方法结合电子密度自洽对顺磁相进行了研究。在顺磁相中的关联Mn 3d轨道的重整化因子一般小于BaFe_{2} As_{2}，这表明BaMn_{2} As_{2}比BaFe_{2} As_{2}具有更强的电子关联效应.与d-模型相比，ddp模型的结果向J侧耦合的Hund规则的系统偏移表明，主要As 4p电子对Fe/Mn 3d电子的屏蔽效应是明显的。对于实验磁矩小的BaFe_{2} As_{2}模型，随着J的增加，从顺磁态到反铁磁基态的跃迁逐渐增加;而对于实验磁矩大的BaMn_{2} As_{2}模型，随着J的增加，从顺磁态到反铁磁基态的跃迁则急剧增加.这两个系统之间的关键区别是d级占领。BaMn_{2} As_{2}，每个Mn原子大约有5个d-电子，对于相同的电子相关值，比BaFe_{2} As_{2}更接近到Mott绝缘态的跃迁。在这里，一个轨道选择性的过渡，需要一个系统与接近6个电子只发生在显着较大的值的库仑相互作用。
英文摘要：
To elucidate the role played by the transition metal ion in the pnictide materials, we compare the electronic and magnetic properties of BaFe_{2}As_{2} with BaMn_{2}As_{2}. To this end we employ the LDA+Gutzwiller method to analyze the mass renormalizations and the size of the ordered magnetic moment of the two systems. We study a model that contains all five transition metal 3d orbitals together with the Ba-5d and As-4p states (ddp-model) and compare these results with a downfolded model that consists of Fe/Mn d-states only (d-model). Electronic correlations are treated using the multiband Gutzwiller approximation. The paramagnetic phase has also been investigated using LDA+Gutzwiller method with electron density self-consistency. The renormalization factors for the correlated Mn 3d orbitals in the paramagnetic phase of BaMn_{2}As_{2} are shown to be generally smaller than those of BaFe_{2}As_{2}, which indicates that BaMn_{2}As_{2} has stronger electron correlation effect than BaFe_{2}As_{2}. The screening effect of the main As 4p electrons to the correlated Fe/Mn 3d electrons is evident by the systematic shift of the results to larger Hund's rule coupling J side from the ddp-model compared with those from the d-model. A gradual transition from paramagnetic state to the antiferromagnetic ground state with increasing J is obtained for the models of BaFe_{2}As_{2} which has a small experimental magnetic moment; while a rather sharp jump occurs for the models of BaMn_{2}As_{2}, which has a large experimental magnetic moment. The key difference between the two systems is shown to be the d-level occupation. BaMn_{2}As_{2}, with approximately five d-electrons per Mn atom, is for same values of the electron correlations closer to the transition to a Mott insulating state than BaFe_{2}As_{2}. Here an orbitally selective transition, required for a system with close to six electrons only occurs at significantly larger values for the Coulomb interactions.
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