Momentum-Resolved Signatures of Carrier Screening Effects on Electron-Phonon Coupling in MoS₂

Electron-phonon coupling is central to many condensed matter phenomena. Harnessing these effects for functionality in materials always involves nonequilibrium electronic states, which in turn alter quasi-free-carrier density and screening. Thus, gaining a fundamental understanding of the interplay of carrier screening and electron-phonon coupling is essential for advancing ultrafast science. Prior work has mainly focused on the impact of carrier screening on electronic structure properties. Here, we investigate the nonequilibrium lattice dynamics of MoS₂ after a photoinduced Mott transition. The experimental data are closely reproduced by ab initio ultrafast dynamics simulations. We find that the nonthermal diffuse scattering signals in the vicinity of the Bragg peaks, originating from long-wavelength phonon emission, can only be reproduced upon explicitly accounting for the screening of electron-phonon interaction introduced by the Mott transition. These results indicate that carrier screening influences electron-phonon coupling, leading to a suppression of intravalley phonon-assisted carrier relaxation. Overall, the combined experimental and computational approaches introduced here offer prospects for exploring the influence of screening of the electron-phonon interactions and relaxation pathways in driven solids.