title: Evidence of delocalized excitons in amorphous solids.
abstract: We studied the temperature dependence of the absorption coefficient of amorphous SiO2 in the range from 8 to 17.5 eV obtained by Kramers-Kronig dispersion analysis of reflectivity spectra. We demonstrate the main excitonic resonance at 10.4 eV to feature a close Lorentzian shape redshifting with increasing temperature. This provides a strong evidence of excitons being delocalized notwithstanding the structural disorder intrinsic to amorphous SiO2. Excitons turn out to be coupled to an average phonon mode of 83 meV energy.
authors.affiliation: Dipartimento di Scienze Fisiche ed Astronomiche, Università degli Studi di Palermo, Via Archirafi 36, I-90123 Palermo, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Messina
authors.forename: Eleonora
authors.initials: E
authors.lastname: Vella
authors.forename: Marco
authors.initials: M
authors.lastname: Cannas
authors.forename: Roberto
authors.initials: R
authors.lastname: Boscaino