Coulomb and electron–phonon interactions and doping effects in \(\text {KNi}_2\text {Se}_2\) crystal

Abstract

Using density functional theory combined with dynamical mean-field theory (DFT+DMFT), we explore the correlated electronic structure of the \(\text {KNi}_2\text {Se}_2\) superconductor and analyze how its paramagnetic normal state spectra is modified by electron–electron interactions and electron/hole doping. We demonstrate the emergence of orbital selectivity, characterized by the coexistence of Mott-localized states, pseudogapped spectral features, and narrow Kondo-like quasiparticle excitations. In addition, we investigate the interplay between on-site Coulomb interactions and electron–phonon coupling in both pristine and doped \(\text {KNi}_2\text {Se}_2\). Our results reveal that the combination of these interactions gives rise to low-energy electron bound states. These findings provide microscopic insight into the heavy-electron normal state of \(\text {KNi}_2\text {Se}_2\) and contribute to a deeper understanding of the coupled roles of dynamical electronic correlations, electron–phonon interactions, and band filling in shaping the normal state properties of unconventional multi-orbital superconductors.