Giant binding ofD−centers in polar crystals

Abstract

It is shown that, due to the electron-LO phonon interaction, the ratio of the binding energy of $D^{-}$ ions to that of donors ($D^0$) can be as much as an order of magnitude greater in strongly polar materials than in nonpolar crystals. A key role in the binding enhancement is played by the attraction between the electrons and the static polarization charge which they induce near the center of the ion. Estimates are given for $D^{-}$ binding energies in AgBr and AgCl.