Hybridization strength

The calculation of the core levels of LajCuO discussed above was performed within the cluster approximation wherein the dependence of the spectral shape on the oxygen band-width is missed out. In order to include the effect of the oxygen 2p derived band on the spectral shape, the core-level photoemission calculation has to be performed within the impurity model which includes the O 2p band-width (instead of a single O 2p level). For reasonable values of the hybridization strength, t, the range of values of A is such that the Cu appears close to the bottom of the... 

In figure 31, we show the variation of the calculated/s//m with A/tpd, where increases with increasing J/ipd. At large values of tpA, the variation of IJIm with A/tpA becomes less pronounced the dependence of /s//m on A appears to be more pronounced when tpA is small. In this context, we note that the experimental/s//m values for La2 3.Sr3.CuO4... 

X-edge absorption spectra of 3d and 4d metals (205,206) show similar XANES for metals with similar crystal structure. After recalibration of the energy scales, in order to remove the trivial kinetic energy dependence on lattice spacing, the observed peak positions are a signature of the environment of the absorber as determined by local geometry only. The amplitude of features due to specific bands are proportional to the hybridization strength or wave character (204). 

Fig. 46. Spectral density P4, of 4f 4f excitations for a degeneracy of JV = 6 with parameters W/r — 10, lEfl/r = 2. Here f = = Nf, where Vis the rescaled hybridization strength in eq.

Microscopically, an important contribution to the Griineisen parameter coupling in HF Ce compounds comes from a strong volume dependence of the sf-hybridization strength V k) (Allen and Martin 1982, Razafimandimby et al. 1984). Therefore, sound waves of compressional character, e.g., longitudinal modes modulate the mixing term in the Hamiltonian of eq. (107) and consequently couple to electronic states. For smaU displacements one can write... 

In the spirit of a unified picture for IV and heavy-fermion phenomena, which has been promoted above, we ascribe elastic anomalies in these systems to a dependence of basic electronic parameters, like the position of f-levels and their hybridization strength with band states, upon the location of neighbouring atoms in the crystal. An expansion of the form (Grewe et al. 1980)... 

In addition to the information on the valence state the Lm absorption of Ce as function of volume yields distinct information on the final-state problem. If the 4f conduction electron hybridization strength would be volume-dependent, the shake up intensity at the leading edge of the trivalent absorption line should increase with pressure. The 2p binding energy shift of the hypothetical divalent shake up from... 

There is strong evidence that the observation of intermultiplet transitions is related to the hybridization strength of the corresponding 4f" configuration. In the case of Ce (Yb) this can be qualitatively described by the Kondo temperature Tic or by the valence fluctuating temperature Typ- More care is necessary for Eu and Sm. If the valence is close to the 4f ... 

J hybridization strength between f elec- Po residual electrical resistivity... 

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