Extended Data Fig. 2: Reflectivity spectra at different impurity scattering rates.
From: Born effective charges and vibrational spectra in superconducting and bad conducting metals
Reflectivity spectra at different impurity scattering rates (a) Superconducting and (b) normal phase reflectivity spectra, where the self-energy is evaluated with the procedure explained in the Supplementary Section VI for three different impurity scattering rates ηimp. In the left panel the offset is 0 for ηimp = 28 meV, 0.01 for ηimp = 135 meV and 0.02 for ηimp = 200 meV. The impurity scattering rate affects differently the electronic baseline and the vibrational resonances. In the superconducting phase higher impurity scattering rates correspond to sharper drops of the reflectivity for ℏω ~ 2Δ, while in the normal phase they correspond to vertical shifts of the electronic baseline. The intensity of the vibrational resonances is enhanced by an increase of impurity scattering rates in both cases, while their shape is affected in a less trivial way due to the interplay between electronic and lattice responses, as manifested by the different effects upon the two resonances centered around 84 and 148 meV.
