Ultrafast Modulation of Electron-Phonon Couplings and Phonon-Mediated Superconductivity

Ultrafast modulation of electron-phonon couplings via laser excitation has been experimentally demonstrated, yet a clear microscopic understanding remains elusive. Here, we establish the first ab initio framework combining time-dependent density-functional theory, density-functional perturbation theory, and Migdal-Eliashberg theory to track electron-phonon couplings and superconductivity in prototypical phonon-mediated superconductor MgB_{2} under laser illumination. We find that near-infrared laser pulses induce charge transfer from boron σ to π orbitals, effectively renormalizing the electron-phonon couplings and boosting the superconducting critical temperature to ∼52  K. The simulated thermalized superconducting gaps match well with experimental measurements. We propose a generalizable route for ultrafast modulation of superconductivity in materials whose dominant electron-phonon coupling channel can be selectively addressed by light, with photoinduced changes in electronic coupling and screening playing a central role. This Letter offers fundamental insight into nonequilibrium optical control of electron-phonon interactions and superconductivity, and provides a predictive tool for studying photo-modulated electron-phonon coupling and macroscopically observable superconducting properties.