A magnetic impurity embedded in a Fermi sea is collectively screened by a cloud of conduction electrons to form a Kondo singlet below a characteristic energy scale T_K, the Kondo temperature, through the mechanism of the Kondo effect. We have reinvestigated the Kondo singlet by means of the newly developed natural orbitals renormalization group (NORG) method. We find that, in the framework of natural orbitals formalism, the Kondo screening mechanism becomes transparent and simple, while the intrinsic structure of a Kondo singlet is clearly resolved. For a single impurity Kondo system in whichever case of either finite size or thermodynamic limit, there exists a single active natural orbital that screens the magnetic impurity dominantly. In the perspective of entanglement, the magnetic impurity is entangled dominantly with the active natural orbital, i.e., the subsystem formed by the active natural orbital and the magnetic impurity basically disentangles from the remaining system. We have also studied the structures of the active natural orbital respectively projected into real space and momentum space. Moreover, the dynamical properties, represented by one-particle Green’s functions defined at the active natural orbital, are obtained by the correction vector method. Meanwhile, the well-known Kondo resonance is clearly observed in the spectral function at the active natural orbital. To realize the thermodynamic limit, the Wilson chains with the numerical renormalization group approach are employed.

中文翻译：

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近藤单峰的自然轨道重归一化组方法

嵌入费米海中的磁性杂质被导电电子云共同屏蔽，以形成低于特征能级T _K的近藤单线态，近藤温度，通过近藤效应的机制。我们通过新开发的自然轨道重归一化组（NORG）方法对近藤单重态进行了重新研究。我们发现，在自然轨道形式主义的框架下，近藤筛选机制变得透明和简单，而近藤单线态的内在结构得到了明确解决。对于单一杂质近藤系统，无论大小或热力学极限如何，都存在一个主动的自然轨道，该轨道自然地屏蔽了磁性杂质。从纠缠的角度来看，磁性杂质主要与活动的自然轨道纠缠在一起，即，由活动的自然轨道形成的子系统和磁性杂质基本上与其余系统脱离纠缠。我们还研究了分别投射到真实空间和动量空间中的活动自然轨道的结构。此外，通过校正矢量方法获得了由在活性自然轨道上定义的单粒子格林函数表示的动力学特性。同时，在活跃的自然轨道的光谱函数中清楚地看到了众所周知的近藤共振。为了实现热力学极限，采用了具有数值重归一化组方法的威尔逊链。在活跃的自然轨道的光谱函数中可以清楚地看到众所周知的近藤共振。为了实现热力学极限，采用了采用数值归一化群方法的威尔逊链。在活跃的自然轨道的光谱函数中可以清楚地看到众所周知的近藤共振。为了实现热力学极限，采用了采用数值归一化群方法的威尔逊链。