Exchange interaction in the yellow exciton series of cuprous oxide

TL;DR

This study combines experimental and numerical methods to analyze the exchange interaction in yellow excitons of cuprous oxide, revealing phenomena like exciton state reversal and deviations from hydrogenic models.

Contribution

It provides a detailed numerical interpretation of experimental observations, including state reversal and exchange splitting behavior, considering complex band structure and central-cell effects.

Findings

Reversal of ortho- and paraexciton states for 2S yellow exciton

Deviation of exchange splitting from n^{-3} law

Green 1S exciton exchange splitting exceeds twice that of yellow 1S

Abstract

We experimentally and numerically investigate the exchange interaction of the yellow excitons in cuprous oxide. By varying the material parameters in the numerical calculations, we can interpret experimental findings and understand their origin in the complex band structure and central-cell corrections. In particular, we experimentally observe the reversal of the ortho- and paraexciton for the $2S$ yellow exciton, and explain this phenomenon by an avoided crossing with the green $1S$ orthoexciton in a detailed numerical analysis. Furthermore, we discuss the exchange splitting as a function of the principal quantum number $n$ and its deviation from the $n^{-3}$ behavior expected from a hydrogenlike model. We also explain why the observed exchange splitting of the green $1S$ exciton is more than twice the splitting of the yellow $1S$ state.