The Effects of Band Dispersion and Interactions on the Excitation Gaps in the Periodic Anderson Model in infinite Dimensions : Condensed Matter: Electronic Properties, etc.

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We investigate the inter-play of f-electron band dispersion and inter-f electron interactions on the gap in the one electron density of states (DOS) of the periodic Anderson model. The calculations are based on dynamical mean field theory and the numerical renorrmalization group method for the model in infinite dimensions. The local f-electron DOS at low energies for the electron-hole symmetric model with interactions is found to have a complete-gap, a pseudo-gap or to be gap-less, whenever these structures occur for the non-interaction model but the parameters that characterize these features are strongly renormalized. As the degree of f-electron dispersion is increased, when there is a complete gap, the many-body renormalization remains almost constant, but in the pseudo-gap case the renormalization remains almost constant, but in the pseudo-gap case the renormalization increases. We calculated the sizes of gaps both in the pseudo-gap case the renormalization increases. When the gap width is defined by the edges in the spectrum for the complete-gap model, the widths of the indirect gap and the spin gap are equal, independent of the degree of electron correlation. However, if the with is defined as the excitation energy between the peaks in the spectrum, then the ratio of the indirect gap to the spin gap increases and eventually saturates as the correlation increases. The value of this ratio depends on the f-electron band dispersion. We have also investigated the dependence of the shape of the interacting DOS on the f-band filling for different forms of f-band dispersion. When the f-band dispersion is small, the gap structure in the symmetric model vanishes as the filling factor decreases. When the model, including the dispersion, has no gap structure, the filling dependence on the DOS in low energies is similar to that for a single impurity Anderson model. The energy dispersion of the quasi-particle in the range, _f < < _f + U, is approximately explained by the renormalized band model in the cases of both large and small f-band dispersion.
社団法人日本物理学会の論文
2000-06-15

The Effects of Band Dispersion and Interactions on the Excitation Gaps in the Periodic Anderson Model in infinite Dimensions : Condensed Matter: Electronic Properties, etc.

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