We have studied the angular (at 1.8 K) and temperature dependence (from 1.8 to 70 K) of the time-integrated luminescence spectra of 1s orthoexcitons from the yellow series in Cu2O arising from resonant two-photon pumping to both the 1s and 2s levels. For resonant pumping to the 1s level, the direct (denoted as Xo) emission is strongly enhanced at low temperature. It is forward directed, however, with an angular width substantially larger than the divergence of the excitation beam; excitation to the 2s level (which subsequently decays into a 1s level) results in a more isotropic angular distribution of Xo emission. The lifetime of the Xo emission resulting from resonant excitation to the 1s level at 1.8 K is ∼2 ns, shorter than the decay time of thermalized orthoexcitons. The results support the idea that resonant two-photon excitation to the 1s level results primarily in a quadrupole-orthoexciton-polariton formation, whereas 2s excitation does not. The behavior of the phonon-assisted luminescence is essentially independent of the mode of excitation.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 2001|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics