Electronic Raman scattering and the renormalization of the electron spectrum in LuB12

The electronic Raman scattering in LuB12 single crystals of various isotope compositions is studied in the temperature range 10–650 K. The shape and the energy position of spectral maxima depend on the direction and magnitude of a probe wavevector, the temperature, and the excitation symmetry and remain unchanged when the isotope composition changes. Experimental spectra are compared with the spectra simulated on the basis of a calculated electronic structure. The experimental results are successfully described when the electron spectrum renormalization effects caused by electron–phonon coupling are taken into account. This confirms that the origin of the observed spectra in LuB12 is due to Raman scattering by electrons. A comparison of the calculated and experimental data makes it possible to determine the coupling constant (λ ep = 0.32) that gives the correct superconducting transition temperature.