Observation of high angular momentum excitons in cuprous oxide

TL;DR

This paper reports the observation of high angular momentum excitons in cuprous oxide, revealing deviations from hydrogen-like models due to cubic symmetry breaking, and provides detailed experimental and theoretical analysis of these states.

Contribution

It demonstrates the mixing of high angular momentum excitons with P-excitons caused by symmetry breaking and determines the cubic anisotropy parameter through combined experimental and theoretical work.

Findings

Observation of F- and H-excitons in absorption spectra.

Three-fold splitting of F-excitons depending on principal quantum number.

Determination of the cubic anisotropy parameter of Cu₂O.

Abstract

The recent observation of dipole-allowed $P$-excitons up to principal quantum numbers of $n=25$ in cuprous oxide has given insight into exciton states with unprecedented spectral resolution. While so far the exciton description as a hydrogen-like complex has been sufficient for cubic crystals, we demonstrate here distinct deviations: The breaking of rotational symmetry leads to mixing of high angular momentum $F$- and $H$-excitons with the $P$-excitons so that they can be observed in absorption. The $F$-excitons show a three-fold splitting that depends systematically on $n$, in agreement with theoretical considerations. From detailed comparison of experiment and theory we determine the cubic anisotropy parameter of the Cu$_2$O valence band.