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On X-ray-singularities in the f-electron spectral function of the Falicov-Kimball model

Frithjof B. Anders·G. Czycholl
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Abstract

The f-electron spectral function of the Falicov-Kimball model is calculated within the dynamical mean-field theory using the numerical renormalization group method as the impurity solver. Both the Bethe lattice and the hypercubic lattice are considered at half filling. For small U we obtain a single-peaked f-electron spectral function, which --for zero temperature-- exhibits an algebraic (X-ray) singularity ($|ω|^{-α}$) for $ω\to 0$. The characteristic exponent $α$ depends on the Coulomb (Hubbard) correlation U. This X-ray singularity cannot be observed when using alternative (Keldysh-based) many-body approaches. With increasing U, $α$ decreases and vanishes for sufficiently large U when the f-electron spectral function develops a gap and a two-peak structure (metal-insulator transition).

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Frithjof B. Anders, G. Czycholl. 2004-11-29. On X-ray-singularities in the f-electron spectral function of the Falicov-Kimball model. https://doi.org/10.1103/physrevb.71.125101

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