A temperature study of high‐n Rydberg states in Cu2O

Abstract

The temperature dependence of Rydberg excitons in Cu_2O with principal quantum numbers n≥ 10 is investigated for bath temperatures between 1.3 and 50 K. The energy shift of Rydberg exciton lines allows us to perform a precise measurement of the Cu_2O band gap as a function of temperature. The Γ^−_5 phonon shows a dominant contribution to the temperature shift of the band gap. The optical properties of Rydberg excitons are analyzed for different temperatures and discussed in the context of phonon scattering as well as thermal ionization of impurities and compared to earlier descriptions in Ref. [1]. The maximum principal quantum number n_max as a function of temperature in crystals of different quality is studied and compared. The observations are correlated to photoluminescence spectra of impurities at different temperatures.