Highly-excited Rydberg excitons in synthetic thin-film cuprous oxide

Abstract

Cuprous oxide (Cu2O) has recently emerged as a promising material in solid-state quantum technology, specifically for its excitonic Rydberg states characterized by large principal quantum numbers (n). The significant wavefunction size of these highly-excited states (proportional to n2) enables strong long-range dipole-dipole (proportional to n4) and van der Waals interactions (proportional to n11). Currently, the highest-lying Rydberg states are found in naturally occurring Cu2O. However, for technological applications, the ability to grow high-quality synthetic samples is essential. The fabrication of thin-film Cu2O samples is of particular interest as they hold potential for observing extreme single-photon nonlinearities through the Rydberg blockade. Nevertheless, due to the susceptibility of high-lying states to charged impurities, growing synthetic samples of sufficient quality poses a substantial challenge. This study successfully demonstrates the CMOS-compatible synthesis of a Cu2O thin film on a transparent substrate that showcases Rydberg excitons up to n=8 which is readily suitable for photonic device fabrications. These findings mark a significant advancement towards the realization of scalable and on-chip integrable Rydberg quantum technologies.