Rydberg Excitons in Synthetic Cuprous Oxide (Cu$_2$O)

TL;DR

This study investigates high-lying Rydberg excitons in synthetic cuprous oxide, comparing it with natural samples, and explores its potential for scalable quantum devices through detailed optical and structural analysis.

Contribution

It demonstrates the presence of Rydberg excitons up to n=10 in synthetic Cu$_2$O and analyzes their properties, highlighting differences from natural samples and implications for quantum technology.

Findings

Synthetic Cu$_2$O shows Rydberg excitons up to n=10.

Synthetic samples have more copper vacancies and inhomogeneity.

Optical properties are similar between synthetic and natural samples.

Abstract

High-lying Rydberg states of Mott-Wannier excitons are receiving considerable interest due to the possibility of adding long-range interactions to the physics of exciton-polaritons. Here, we study Rydberg excitation in bulk synthetic cuprous oxide grown by the optical float zone technique and compare the result with natural samples. X-ray characterization confirms both materials are mostly single crystal, and mid-infrared transmission spectroscopy revealed little difference between synthetic and natural material. The synthetic samples show principal quantum numbers up to $n=10$, exhibit additional absorption lines, plus enhanced spatial broadening and spatial inhomogeneity. Room temperature and cryogenic photoluminescence measurements reveal a significant excess of copper vacancies in the synthetic material. These measurements provide a route towards achieving \mbox{high-$n$} excitons in synthetic crystals, opening a route to scalable quantum devices.