Electron-electron versus electron-phonon interactions in lattice models: Screening effects described by a density functional theory approach

We address the interplay of electron-electron (e-e) and electron-phonon (e-ph) interactions in the Hubbard- Holstein model, using a two-component density functional theory. Exchange-correlation potentials constructed via dynamical mean field theory for a D = ∞ Bethe lattice and analytically for an isolated site give a new perspective on e-ph screening of the e-e interactions and its effect on the charge- and spin-Kondo regimes. Comparisons to exact benchmarks show that the approach is suitable to describe transport properties and real- time dynamics in homogeneous and inhomogeneous lattice systems.