We now briefly discuss the electronic background in the Raman spectra, which has been assigned to hot carrier luminescence34. Figure 2(d) inset shows that the background starts to increase at t = −200 fs and reaches its maximum at t ~ 0 fs, when the G-phonons begin to appear. The background then decreases to the initial level at t = 300 fs, while the phonon intensity keeps increasing from t = 0 fs to t = 300 fs. This behavior reflects changes in electronic temperature and is consistent with previous reports34353637. However, it is not possible to read out instantaneous electronic temperatures from the observed intensities.