Electron-phonon interaction and spectral weight transfer inFe1−xCoxSi

摘要: A comprehensive ellipsometric study was performed on Fe$_{1-x}$Co$_{x}$Si single crystals in the spectral range from 0.01 eV to 6.2 eV. Direct and indirect band gaps of 73 meV 10 meV, respectively, were observed FeSi at 7 K. One four infrared-active phonons that is energetically close direct absorption edge coupled both electrons low-energy phonon. This evident asymmetry phonon line shape a reduction its frequency when shifts across energy due temperature dependence gap. As increases, gap changes sign, which manifests as transition semiconductor semimetal. The corresponding gain weight low energies recovered within an several present findings strongly support model indicating can be well described itinerant picture, taking into account self-energy corrections.