Photogeneration and signatures of coherent phonons in time-resolved photoemission spectroscopy: First-principles time-dependent adiabatic GW approach

Abstract

Coherent lattice dynamics can be observed in pump-probe time-resolved and angle-resolved photoemission spectroscopy (TR-ARPES) as a periodic modulation of intensity and energy of photoelectrons over probe time. We present an ab initio time-dependent GW approach including electron-phonon (e-ph) couplings to simulate the photogeneration of coherent phonons and their effects on the TR-ARPES of monolayer MoS2. We demonstrate that state-resolved e-ph coupling strength can be obtained from analyzing coherent phonon modulations on TR-ARPES. Features of both the impulsive stimulated Raman scattering mechanism and the displacive excitation mechanism of coherent phonon generation are identified in our simulations. We clarify their origins and the coincident selection rule of coherent phonon generation and Raman scattering intensity. This method provides supports to analyze coherent phonon dynamics and e-ph couplings in TR-ARPES and enables quantitative engineering of band structure through coherent phonons.