Kondo hybridization

The low ordering temperatures and low moments are explained by a competition of RKKY exchange with Kondo hybridization (Bonviiie et al. 1988). 

Sugiura T, Kodaka T, Kondo S, Tonegawa T, Nakane S, Kishimoto S, Yamashita A, Waku K (1996) 2-Arachidonoylglycerol, a putative endogenous cannabinoid receptor ligand, induces rapid, transient elevation of intracellular free Ca2+ in neuroblastoma x glioma hybrid NG108-15 cells. Biochem Biophys Res Commun 229 58-64... 

This variation can be seen in Figure 11.8a. As noted by Neumann and Fulde, a requirement for experimentally observable Kondo effects is significant orbital hybridization between ligand and metal, that is, ligand donation into bonding orbitals. A multi-configurational wavefunction, however, is extremely flexible. 

The distinction between Kondo metals, etc. and HF systems is fuzzy at best. As pointed out, the Kondo interaction is, among others, a basic ingredient of HF behavior. In a Kondo-lattice material one observes the effects of the Kondo interaction, for example on the magnetic properties, but very heavy quasiparticles are not formed and in consequence, the Sommerfeld constant is only slightly enhanced, That at least is the basis for a distinction we shall adopt. The hybridization between 4f and conduction electrons can lead to a hybridization gap in the density of states at the Fermi surface. The exact mechanism of gap formation is still under debate and also may vary from compound to compound. If a gap is present, one leaves the realm of Kondo metals and has, depending on the form of the gap (e.g., whether it is open in all crystallographic directions) and on its width, either a Kondo semimetal, semiconductor or insulator. The latter are certainly the most challenging class of Kondo compounds to understand. 

Trivalent intermetaUic [Xe]4f ytterbium compounds are particularly important for comparison with cerium compounds, since they exhibit the f-hole analog of [Xe]4f cerium. In principle, the Kondo effect should be symmetrical between electrons and holes. The maia mechanism determining the ground-state behavior in cerium and ytterbium intermetaUics is the interaction between the 4f electrons and s, p and d electrons of neighboming ligands. This so-called f—spd hybridization tends to reduce the 4f-level... 

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