Extended Data Fig. 1: Undamped BECs in a wider frequency range.
From: Born effective charges and vibrational spectra in superconducting and bad conducting metals
The independent components of the undamped dynamical BECs are plotted on their typical variation scale, which is larger than the vibrational frequency range of Fig. 3. In particular, we can notice a strong variation for ℏω > 1 eV due to the onset of interband transitions. This onset is coherent with the reflectivity drop observed at the same energy (Fig. 1a). The real and imaginary parts are shown in panel (a) and (b), respectively.
