Ab initio real-time quantum dynamics of charge carriers in momentum space

Application of the non-adiabatic molecular dynamics (NAMD) approach is limited to studying carrier dynamics in the momentum space, as a supercell is required to sample the phonon excitation and electron–phonon (e–ph) interaction at different momenta in a molecular dynamics simulation. Here we develop an ab initio approach for the real-time charge carrier quantum dynamics in the momentum space (NAMD_k) by directly introducing e–ph coupling into the Hamiltonian based on the harmonic approximation. The NAMD_k approach maintains the zero-point energy and includes memory effects of carrier dynamics. The application of NAMD_k to the hot carrier dynamics in graphene reveals the phonon-specific relaxation mechanism. An energy threshold of 0.2 eV—defined by two optical phonon modes—separates the hot electron relaxation into fast and slow regions with lifetimes of pico- and nanoseconds, respectively. The NAMD_k approach provides an effective tool to understand real-time carrier dynamics in the momentum space for different materials. This study presents an ab initio approach for the real-time charge carrier quantum dynamics in the momentum space, which is computationally more efficient than conventional real-space non-adiabatic molecular dynamics method. The method is applied to study hot carrier dynamics in graphene, which provides insights about the phonon-specific relaxation mechanism.