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首页> 外文期刊>Physical review >Spectral properties of the two-impurity Anderson model with varying distance and various interactions
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Spectral properties of the two-impurity Anderson model with varying distance and various interactions

机译：可变距离和各种相互作用的二杂质安德森模型的光谱性质

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We present an approximation for the treatment of two interacting magnetic impurities immersed into a noninteracting metallic host. The scheme is based on direct perturbation theory with respect to the hybridization between the impurity and band electrons. This two-impurity enhanced noncrossing approximation can fully incorporate the indirect interactions between the impurities that are mediated by the conduction electrons as well as additional arbitrary direct interaction matrix elements. We qualify the approximation by investigating the uncoupled case and conclude that the two-impurity approximation is equally accurate as its single-impurity counterpart. The physical properties of the two-impurity Anderson model are first investigated in some limiting cases. In a regime where each of the uncoupled two impurities would exhibit a pronounced Kondo effect, we ignore the indirect coupling via the conduction band and only incorporate direct interactions. For a ferromagnetic direct exchange coupling, the system displays a behavior similar to a spin-one Kondo effect, while an antiferromagnetic coupling competes with the Kondo effect and produces a pseudogap in the many-body Kondo resonance of the single-particle spectral function. Interestingly, a direct one-particle hopping also produces a pseudogap, but additionally pronounced side peaks emerge. This gap is characteristically different from the case with antiferromagnetic coupling since it emerges as a consequence of distinct Kondo effects for the bonding and antibonding orbital, i.e., it reflects a splitting of even and odd parity states. For the general case of only indirect coupling via the conduction band, the results show signatures of all the previously discussed limiting cases as a function of the impurity-impurity distance. Oscillatory behavior in physical quantities is to be expected due to the generated Ruderman-Kittel-Kasuya-Yosida interaction. We are led to the conclusion that the well-known Doniach scenario captures essential aspects of this model, but the details, especially at small distances, are more complicated.
机译：我们为浸入非相互作用金属主体中的两个相互作用的磁性杂质的处理提供了一种近似方法。该方案基于关于杂质和带电子之间的杂化的直接摄动理论。这种两个杂质增强的非交叉近似可以完全纳入由传导电子以及其他任意直接相互作用基质元素介导的杂质之间的间接相互作用。我们通过研究未耦合的情况对近似值进行限定，并得出结论：两个杂质近似值与单个杂质近似值一样准确。首先在某些极限情况下研究了两个杂质的安德森模型的物理性质。在未耦合的两种杂质均会表现出明显的近藤效应的情况下，我们忽略了通过导带的间接耦合，仅结合了直接相互作用。对于铁磁直接交换耦合，系统显示出类似于自旋近藤效应的行为，而反铁磁耦合与近藤效应竞争，并在单粒子光谱函数的多体近藤共振中产生伪间隙。有趣的是，直接的单粒子跳跃也会产生伪间隙，但另外会出现明显的侧峰。该间隙在特征上与反铁磁耦合的情况不同，因为该间隙是由于键合和反键合轨道具有独特的近藤效应而出现的，即，它反映了偶数和奇数奇偶状态的分裂。对于仅通过导带间接耦合的一般情况，结果显示了所有先前讨论的极限情况的特征，它们是杂质-杂质距离的函数。由于产生了Ruderman-Kittel-Kasuya-Yosida相互作用，因此可以预期物理量的振荡行为。我们得出的结论是，众所周知的Doniach场景捕获了该模型的基本方面，但是细节（尤其是在小距离的情况下）更加复杂。

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