Attosecond screening dynamics mediated by electron localization in transition metals

Transition metals, with their densely confined and strongly coupled valence electrons, are key constituents of many materials with unconventional properties 1 , such as high-temperature superconductors, Mott insulators and transition metal dichalcogenides 2 . Strong interaction offers a fast and efficient lever to manipulate electron properties with light, creating promising potential for next-generation electronics 3 – 6 . However, the underlying dynamics is a hard-to-understand, fast and intricate interplay of polarization and screening effects, which are hidden below the femtosecond timescale of electronic thermalization that follows photoexcitation 7 . Here, we investigate the many-body electron dynamics in transition metals before thermalization sets in. We combine the sensitivity of intra-shell transitions to screening effects 8 with attosecond time resolution to uncover the interplay of photo-absorption and screening. First-principles time-dependent calculations allow us to assign our experimental observations to ultrafast electronic localization on d orbitals. The latter modifies the electronic structure as well as the collective dynamic response of the system on a timescale much faster than the light-field cycle. Our results demonstrate a possibility for steering the electronic properties of solids before electron thermalization. We anticipate that our study may facilitate further investigations of electronic phase transitions, laser–metal interactions and photo-absorption in correlated-electron systems on their natural timescales. Experiments with attosecond time resolution reveal many-body electron dynamics in transition metals before thermalization sets in. Ultrafast electronic localization on d orbitals is found to dominate the collective dynamic response of the system.