Electronic Raman scattering and the electron–phonon interaction in YB6

Electronic Raman scattering in YB 6 and in its structural and electronic analog LaB 6 has been studied in the temperature range of 10–730 K. The experimental spectra have been compared to those calculated on the basis of ab initio band structures with renormalization owing to the electron–phonon interaction. Good agreement between the calculation and experiment for LaB 6 has been obtained throughout the entire temperature range. This allows the determination of the coupling constant λ ep = 0.25. To satisfactorily describe the spectra of electronic light scattering in YB 6 , it is necessary to introduce an additional electron relaxation channel. In this case, the estimate of the electron–phonon coupling constant λ ep is no more than 0.4; for this reason, a high superconducting transition temperature cannot be explained only by the phonon mechanism.