Transient excitonic states in noble metals and Al -: art. no. 113112

Bound states between electrons and holes, so-called excitons, are an ubiquitous feature in the spectra of excited states of molecules, clusters, and in a variety of solids such as semiconductors or ionic solids. It is common wisdom that excitons do not exist in metals because the attractive, long-range particle-hole interaction which is needed for the formation of an exciton does not exist in metals due to almost complete screening. We showed in a previous publication that excitons in metals can exist as transient states right after the creation of the electron-hole pair which explained in a natural way the up to then not understood transitions seen in Cu in the experimental spectra of time-resolved two-photon photoemission spectroscopy. In this paper we report about transient excitonic states in Ag and Au. We explain why these states have not yet been detected in Ag but we predict their existence. We show furthermore why transient excitonic states cannot be built up in Al.