Electron-phonon interaction and spectral weight transfer in Fe$ {1-x}$Co$ {x}$Si - Condensed Matter > Materials ScienceReport as inadecuate




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Abstract: A comprehensive ellipsometric study was performed on Fe$ {1-x}$Co$ {x}$Sisingle crystals in the spectral range from 0.01 eV to 6.2 eV. Direct andindirect band gaps of 73 meV and 10 meV, respectively, were observed in FeSi at7 K. One of four infrared-active phonons that is energetically close to thedirect absorption edge is coupled both to the electrons and to the low-energyphonon. This is evident from asymmetry in the phonon line shape and a reductionof its frequency when the absorption edge shifts across the phonon energy dueto the temperature dependence of the direct band gap. As the temperatureincreases, the indirect gap changes sign, which manifests as a transition froma semiconductor to a semimetal. The corresponding gain of the spectral weightat low energies was recovered within an energy range of several eV. The presentfindings strongly support the model indicating that Fe$ {1-x}$Co$ {x}$Si can bewell described in an itinerant picture, taking into account self-energycorrections.



Author: D. Menzel, P. Popovich, N. N. Kovaleva, J. Schoenes, K. Doll, A. V. Boris

Source: https://arxiv.org/







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