Magnetic and non-magnetic ground states of the Kondo lattice
Magnetic and non-magnetic ground states of the Kondo lattice
复制标题
近藤晶格的磁性和非磁性基态
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
Erwin Müller
中科院分区：
文献类型：
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作者：
P. Fazekas;Erwin Müller
我们使用变分法研究任意 J/W 和传导电子浓度 nc 的近藤晶格哈密顿量的基态相图（J 是近藤耦合，W 是带宽）。我们对以下问题特别感兴趣：在什么情况下，全局单重态（集体近藤）费米液体型基态对于磁有序变得不稳定。对于集体近藤单线态，我们使用 Yosida 波函数的晶格推广，这意味着根据 Luttinger 定理存在大费米体积。使用 Gutzwiller 近似，我们得出了任意 J/W 和 nc 处的基态能量以及 nc=1 处的近藤能隙的闭合形式结果。我们引入简单的试验状态来描述小 J (RKKY) 区域中的铁磁、反铁磁和螺旋排序，以及大 J/W 下的长冈型铁磁性。我们研究了三种特殊情况：具有恒定态密度的能带、（紧束缚）线性链和方晶格周期近藤模型。我们发现，费米液态理论中描述的近藤效应的晶格增强，将 RKKY 到非磁性相界推至比之前认为的小得多的 J/W 值。在我们对方晶格情况的研究中，我们还发现了一个大J/W fornc ≤1/3的巡回长冈型铁磁性区域。
We use the variational method to investigate the ground state phase diagram of the Kondo lattice Hamiltonian for arbitraryJ/W, and conduction electron concentrationnc (J is the Kondo coupling andW the bandwidth). We are particularly interested in the question under which circumstances the globally singlet (collective Kondo) Fermi liquid type ground state becomes unstable against magnetic ordering. For the collective Kondo singlet we use the lattice generalization of Yosida's wavefunction which implies the existence of a large Fermi volume, in accordance with Luttinger's theorem. Using the Gutzwiller approximation, we derive closed-form results for the ground state energy at arbitraryJ/W andnc, and for the Kondo gap atnc=1. We introduce simple trial states to describe ferromagnetic, antiferromagnetic, and spiral ordering in the small-J (RKKY) regime, and Nagaoka type ferromagnetism at largeJ/W. We study three particular cases: a band with a constant density of states, and the (tight binding) linear chain, and square lattice periodic Kondo models. We find that the lattice enhancement of the Kondo effect, which is described in our theory of the Fermi liquid state, pushes the RKKY-to-nonmagnetic phase boundary to much smaller values ofJ/W than it was previously thought. In our study of the square lattice case, we also find a region of itinerant, Nagaoka-type ferromagnetism at largeJ/W fornc ≦1/3.