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

Abstract

Application of the nonadiabatic molecular dynamics (NAMD) approach is severely limited to studying carrier dynamics in the momentum space, since 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 quantum dynamics for charge carriers in the momentum space (NAMD k) by directly introducing the e-ph coupling into the Hamiltonian based on the harmonic approximation. The NAMD k Article approach maintains the quantum zero-point energy and proper phonon dispersion, and includes memory effects of phonon excitation. 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 strongly coupled to the electrons, separates the hot electron relaxation into fast and slow regions with the lifetimes of pico-and nano-seconds, respectively. The NAMD k approach provides a powerful tool to understand real-time carrier dynamics in the momentum space for different materials.

Nonadiabatic Molecular Dynamics with Non-Condon Effect of Charge Carrier Dynamics

“…29−31 On computing the electron−phonon coupling matrix, recent work has realized surface-hopping-based phonon-resolved multiple k-point NA-MD with a harmonic approximation, incorporating electron−phonon interactions within a unit cell into the supercell Hamiltonian. 32 However, this approach is limited to small systems containing tens of atoms, making it unsuitable for systems with defects 33,34 due to the huge computational demands for calculating the electron−phonon coupling matrix. Furthermore, the harmonic approximation has additional limitations, as this method may not be suitable for soft materials.…”

Twist Angle-Dependent Intervalley Charge Carrier Transfer and Recombination in Bilayer WS2

“…The dynamics are determined by the NA couplings, d ij = − iℏ ⟨ ϕ i | ∇ R | ϕ j ⟩· R ̇, which depend on the overlap of initial and final wave functions, and wave function sensitivity to atomic motions. The NA coupling between different k-points in the electronic Brillouin zone is zero, unless different q-points for phonons are included as well . The current calculation uses a supercell and Brillouin zone folding, ,, as discussed in Section 2 of the Supporting Information.…”

“…Static electronic properties of twisted bilayer TMDs have been reported using experimental and computational methods. The majority of the earlier nonadiabatic (NA) molecular dynamics (MD) modeling of excited state dynamics in TMD heterojunctions did not explicitly consider intervalley processes − until recently . Additional efforts are needed in this direction in order to provide insights into the multiple experimental studies. ,− ,,, Furthermore, the influence of the twist angle in homojunctions on the static electronic structure, light absorption, and interlayer coupling has not been studied in detail.…”

Energy-Conserving and Thermally Corrected Neglect of Back-Reaction Approximation Method for Nonadiabatic Molecular Dynamics

“…Nonadiabatic molecular dynamics (NA-MD) is a widely adopted family of computational methods to model quantum dynamics of excited states in various systems. − The NA-MD simulations have found their use in describing various kinds of processes in many molecular and condensed-matter systems: modeling nonradiative electron–hole recombination and “hot” carrier relaxation in quantum dots and molecular clusters, − nanotubes, , plasmonic systems, or exotic states of matter; modeling photoinduced isomerization and reactive processes in various molecular systems; − and modeling charge transfer and charge carrier trapping processes in 2D materials, − interfaces, ,− ,, organic solids, , and pristine and defect-containing bulk semiconductors. − …”