Highly Excited Rydberg Excitons in Thin-Film Cuprous Oxide

Photons play an important role in quantum technology because they resist environmental perturbation and can be sent over long distances with minimal loss. However, photons do not interact with each other in linear media, making strong photon nonlinearities indispensable for orchestrating many-body phenomena. Rydberg electronic states with high principal quantum numbers provide these nonlinearities via strong interactions facilitated by their extended wavefunctions. Of particular interest are Rydberg excitons in solid-state hosts, which marry the unmatched interaction strengths of Rydberg states with the scalability of solid-state systems. Cuprous oxide (Cu₂O) is an especially promising host whose unique band structure and crystal lattice symmetry allow it to support long-lived, highly excited Rydberg excitons.



Here, we will present our high-resolution spectroscopic characterization of Rydberg excitons in synthetic, thin-film Cu₂O gown on a transparent substrate, demonstrating states up to n = 7. These measurements are a major step forward in solid-state quantum photonics, not only offering a novel platform for studying quantum many-body physics, but also paving the way for future quantum photonic technologies based on nonlinear optical devices, such as single-photon transistors.