Optical Properties of Rydberg Excitons in Cuprous Oxide

Cuprous oxide (Cu₂O) has recently been proposed as a promising solid-state host for ex-
citonic Rydberg states with large principal quantum numbers (n) whose exaggerated wave-
function sizes (∝ n²) facilitate gigantic, resonant dipole-dipole (∝ n⁴) and van der Waals
(∝ n¹¹) interactions, making them an ideal basis for solid-state Rydberg physics and quan-
tum technology. Synthetic, thin-film Cu₂O samples are of particular interest because they
can be made defect-free via carefully controlled fabrication and are, in principle, suitable
for the observation of extreme single-photon nonlinearities caused by Rydberg blockade. In
this work, we present the development of a spectroscopy experiment for characterizing the
behavior of Rydberg excitons and use it to study a synthetic thin film of Cu₂O grown on a
transparent substrate. We present evidence for the presence of states up to n = 8 and conduct
the first temperature-dependent study of Rydberg excitons in a thin film. We also propose
a technique for studying Rydberg-Rydberg interactions via the creation of high exciton den-
sities and establish a set of rate equations for modeling the processes by which excitons are
created, interact with each other, and decay. Finally, we conclude with a discussion of the
project’s outlook, as well as what future work will be undertaken to study the interactions
between Rydberg excitons and utilize them in scalable, integrable, Rydberg-based quantum
devices.