Study of mode-projected electron-phonon coupling in graphite by time -resolved ARPES*

Time-resolved spectroscopies have significantly contributed to the study of the dynamical properties of conventional and quantum materials. By following the dynamics of excited electrons, one can follow the dominant scattering processes and discern the flow of energy from the electronic system to other degrees of freedom. Time and angle-resolved photoemission spectroscopy (TR-ARPES) allow one to access electron dynamics in a momentum resolved way. In this work, a balance of energy and time resolution revealed a peak associated with optical excitation. In addition, we observe quantized energy-loss scattering processes, which comes from the emission of an optical phonon from electrons in the direct-transition peak (DTP). The characteristic time scale associated with the transfer of spectral weight from the DTP to the phonon-scattering-peak can then be directly related to the mode-projected electron-phonon matrix element.