Integrating Phonon Screening in Ab Initio Downfolding: Implications for Electron-Electron Interactions and Superconductivity

Ab initio downfolding is a promising method for studies of strongly-correlated materials based on first principles [1]. Within this approach, electron-electron interactions are typically computed within the constrained random phase approximation to the screened Coulomb interaction. However, lattice screening of the Coulomb interaction can lead to significant changes in electronic properties, as shown recently for excitons [2]. The influence of phonon screening within the context of ab initio downfolding has mostly been overlooked, particularly for systems with long-range electron-phonon coupling. Here we present a theory and computational framework for integrating phonon screening with ab initiodownfolding. Applying this framework to select materials, we show that phonons can lead to a large modification of short- and long-range electron-electron interactions due to a combination of the Frohlich, piezoelectric, and deformation potential mechanisms. We capture cases where phonons lead to overall attractive interactions between electrons, and we discuss implications for superconductivity observed in carrier-doped GeTe and SrTiO₃. Computational resources were provided by NERSC.



[1] Alvertis, Khan, Tubman, arXiv:2409.12237

[2] Alvertis, Haber, Coveney, Li, Louie, Filip, Neaton, Proc. Nat. Acad. Sciences, 121, e2403434121 (2024)