Ab initio electron dynamics in high electric fields: accurate predictions of velocity-field curves

Electron dynamics in external electric fields governs the behavior of solid-state electronic devices. First-principles calculations enable precise predictions of charge transport in low electric fields. However, studies of high-field electron dynamics remain challenging due to a lack of accurate and broadly applicable methods. Here we develop an efficient approach to solve the Boltzmann transport equation in the time domain with both the electric field advection term and ab initio electron-phonon collisions. These simulations provide field-dependent electronic distributions with a femtosecond resolution, allowing us to investigate both ultrafast and steady-state carrier dynamics in electric fields ranging from low to high (>10 kV/cm). The broad capabilities of our approach are demonstrated by computing time-dependent electron occupations and the drift velocity vs. electric field curves in Si, GaAs, and graphene. Our approach allows us to investigate microscopic details of transport in high electric fields, including the dominant electron-phonon scattering mechanisms and valley occupation dynamics. Our work provides a timely, robust, parameter-free method to compute high-field electrical transport, which will be instrumental in advancing the discovery and design of novel electronic materials.