Dynamical Screening in Correlated Electron Materials

We present an efficient method for incorporating a dynamically screened interaction into the single-site dynamical mean field approximation widely used to treat correlation physics. Model system calculations are presented which capture the essential features of the frequency-dependent interactions previously obtained for Gd, Ni, SrVO(3) and other compounds. Dynamical screening is shown to shift the metal-insulator phase boundary, to change the spectral function near the Mott-Hubbard gap edge, and to renormalize the quasiparticle weight. A multipeak spectral function is found, with shakeoff (Hubbard) bands which are generically neither separated by the screened nor by the unscreened interaction energy, implying that the common practice of extracting the Hubbard U from the energies of features in photoemission and inverse photoemission spectra requires reexamination.