Effect of local electron-electron correlation in hydrogen-like impurities in Ge

Abstract

We have studied the electronic and local magnetic structure of the hydrogen interstitial impurity at the tetrahedral site in diamond-structure Ge, using an empirical tight binding + dynamical mean-field-theory approach because within the local-density approximation (LDA) Ge has no gap. We first establish that within LDA the 1s spectral density bifurcates due to entanglement with the four neighboring sp 3 antibonding orbitals, providing an unanticipated richness of behavior in determining under what conditions a local moment hyperdeep donor or Anderson impurity will result, or on the other hand, a gap state might appear. Using a supercell approach, we show that the spectrum, the occupation, and the local moment of the impurity state displays a strong dependence on the strength of the local on-site Coulomb interaction U , the H-Ge hopping amplitude, the depth of the bare 1s energy level H , and we address to some extent the impurity concentration dependence. In the isolated impurity, strong interaction regime a local moment emerges over most of the parameter ranges, indicating magnetic activity, and spectral density structure very near (or in) the gap suggests possible electrical activity in this regime.

Tunable localization in an s-electron Kondo system at room temperature

“…Besides, also the rare-earth hydrides YH x and LaH x are expected to possess strong electron correlations. [13,14] It is further interesting noticing that DMFT calculations of H impurities in Ge 8 and Ge 64 supercells show a split H and Ge hybridized Hubbard band close to ε F , [30] which maybe implies that the class of strongly correlated hydrides is even larger than ones that show a MI transition.…”