Resonant phonon scattering of paraexcitons in ${\text{Cu}}_{2}\text{O}$

Resonant phonon scattering of paraexcitons in ${Cu}_{2} O$

Christian Sandfort, Jan Brandt, Dietmar Fröhlich, Manfred Bayer, and Heinrich Stolz

Phys. Rev. B 78, 045201 – Published 1 July 2008

Abstract

The paraexciton in ${Cu}_{2} O$ is optically forbidden to all orders. By means of a magnetic field, it obtains oscillator strength from the quadrupole allowed orthoexciton. With an external magnetic field, we are able to excite resonantly ultracold paraexcitons. We observe a pronounced resonant Raman signal on top of the luminescence from thermalized paraexcitons. We present the magnetic-field dependence of the $Γ_{3}^{-}$ phonon replica of the paraexciton. In addition, we show the spectra of the $Γ_{2}^{-}$ , $Γ_{4}^{-}$ , and $Γ_{5}^{-}$ phonon sidebands. We are even able to observe two-phonon scattering of the paraexciton.