Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting. It is also a superior material system for quantum optics that enabled the observation of two intriguing phenomena, i.e. Rydberg excitons as solid-state analogue to highly-excited atomic states and dense exciton gases showing quantum degeneracy when approaching the phase transition to Bose-Einstein condensation. Previous experiments focused on natural bulk crystals due to major difficulties in growing high-quality synthetic samples. Here, we present Cu2O microcrystals with excellent optical material quality capable of hosting both quantum-degenerate excitons and excited Rydberg states. Growth of Cu2O with exceedingly low point defect levels was achieved on silicon by a scalable thermal oxidation process compatible with lithographic patterning. Using the latter, we demonstrate Rydberg excitons in site-controlled Cu2O microstructures, paving the way for a plethora of applications in integrated quantum photonics.
@article{arxiv.1902.01853,
title = {Cu$_2$O Microcrystals Grown on Silicon as Platform for Quantum-Degenerate Excitons and Rydberg States},
author = {Stephan Steinhauer and Marijn A. M. Versteegh and André Mysyrowicz and Birgit Kunert and Val Zwiller},
journal= {arXiv preprint arXiv:1902.01853},
year = {2020}
}