Microscopic Origin of Dephasing in Solids from First-Principles Electron-Phonon Interactions

Electron-phonon interactions provide a microscopic origin of effective dephasing in solids within real -time TDDFT via a time-domain Williams-Lax framework. In metals, Drude -like damping emerges from a single disordered configuration; in dielectrics, the same mechanism yields clean high-harmonic spectra without introducing ultrashort phenomenological dephasing times. Mapping supercell dynamics onto a primitive-cell density matrix reveals that dephasing is governed primarily by population dynamics (diagonal elements) rather than by the decay of off-diagonal coherence.