Magneto-absorption spectra of hydrogen-like yellow exciton series in cuprous oxide: excitons in strong magnetic fields

Sergey Artyukhin,Maxim Mostovoy,Marek Potemski,Paul H M Van Loosdrecht,Clément Faugeras,Dmitry Fishman,Alexandre Revcolevschi

doi:10.1038/s41598-018-25486-6

Abstract

We study the absorption spectra of the yellow excitons in Cu2O in high magnetic fields using polarization-resolved optical absorption measurements with a high frequency resolution. We show that the symmetry of the yellow exciton results in unusual selection rules for the optical absorption of polarized light and that the mixing of ortho- and para- excitons in magnetic field is important. The calculation of the energies of the yellow exciton series in strong and weak magnetic field limits suggests that a broad n = 2 line is comprized by two closely overlapping lines, gives a good fit to experimental data and allows to interpret the complex structure of excitonic levels.

Highlights

Cuprous oxide Cu2O was the first material in which Wannier-Mott excitons1 – the electron-hole pairs bound by the Coulomb interaction – were observed
Optical absorption spectra measured in zero fields give information about the excitonic Rydberg constant and the reduced mass of the electron-hole pair
Recent measurements of higher levels n > 5 under magnetic fields up to 7 T compared the scaling of features in absorption spectra of Rydberg excitons in external fields to those of a hydrogen atom

Summary

Introduction

Cuprous oxide Cu2O was the first material in which Wannier-Mott excitons1 – the electron-hole pairs bound by the Coulomb interaction – were observed. These states give rise to hydrogen-like series of absorption lines in the optical absorption spectrum of Cu2O at the photon energies described by the Rydberg formula, En = Egap − RyX/n2, where RyX = 98 meV is the excitonic Rydberg constant and Egap = 2.17 eV is the optical gap. Optical absorption spectra measured in zero fields give information about the excitonic Rydberg constant and the reduced mass of the electron-hole pair. Recent measurements of higher levels n > 5 under magnetic fields up to 7 T compared the scaling of features in absorption spectra of Rydberg excitons in external fields to those of a hydrogen atom. Because of the large dielectric constant and small effective masses of charge carriers in Cu2O, the exciton radius greatly exceeds that of a hydrogen atom, which amplifies the effects of external www.nature.com/scientificreports/

Methods

Results

Conclusion