Deviations of the exciton level spectrum in cuprous oxide from the hydrogen series

TL;DR

This paper investigates how the nonparabolicity of band dispersion in cuprous oxide causes deviations in exciton energy levels from the ideal hydrogen-like spectrum, supported by high-resolution spectroscopy data.

Contribution

It identifies the nonparabolicity of band dispersion as the main factor causing deviations in exciton spectra from hydrogen-like behavior in cuprous oxide.

Findings

Nonparabolic band dispersion significantly affects exciton binding energies.

Experimental data confirms the role of band nonparabolicity in spectral deviations.

Deviations from hydrogen series are primarily due to complex band structure effects.

Abstract

Recent high-resolution absorption spectroscopy on excited excitons in cuprous oxide [Nature (London) 514, 343 (2014)] has revealed significant deviations of their spectrum from that of the ideal hydrogen-like series. Here we show that the complex band dispersion of the crystal, which determines the kinetic energy of electrons and holes, strongly affects the exciton binding energy. Specifically, we show that the nonparabolicity of the band dispersion is the main cause of the deviation from the hydrogen series. Experimental data collected from high-resolution absorption spectroscopy in electric fields validate the assignment of the deviation to the nonparabolicity of the band dispersion.