Figure 3 shows electronic dynamics probed by trARPES. Electronic temperature Tel was determined by fitting the slope of the high energy tail in the momentum-integrated ARPES spectra (Fig. 3 inset). Tel increases rapidly after an optical excitation and reaches 3400 K at t = 100 fs. Tel fits well to a bi-exponential decay with decay times of τfast = 0.35 ps and τslow = 3.5 ps. The decay of Tel has a similar timescale to the one observed by previous photoemission experiments125. We evaluated the ratio of the electronic heat capacity to G-phonon heat capacity (see supplementary) from the electronic temperature and G-phonon temperature. It is one of the parameters in our theoretical model as will be discussed later. The 2D Raman peak also reflects electronic temperature, though it is less precise than trARPES results due to self-pumping and greater statistical error (see Supplementary).