The relation of the broad band with the E2g phonon and superconductivity in the Mg(B1−xCx)2 compound

Abstract We have carried out an extensive micro-Raman study on Mg(B1−xCx)2 single crystals, for carbon concentrations up to x = 0.15 . The E2g symmetry broad band for pure MgB2 at ∼600 cm−1 disappears even for small doping levels ( x = 0.027 ) and two well-defined peaks in the high-energy side of this band play a major role in the Raman spectra of the substituted compounds. We propose that a two-mode behavior of the compound might be present, induced by the coupling of the observed phonons with the electronic bands.