Saddle Points and Stark Ladders: Exact Calculations of Exciton Spectra in Superlattices

TL;DR

This paper introduces an exact computational method for excitonic spectra in superlattices, revealing detailed spectral features, Stark ladder effects, and their experimental agreement.

Contribution

It presents a novel exact calculation technique for excitonic absorption spectra in superlattices, capturing complex spectral features and field effects.

Findings

High-resolution spectra show saddle point exciton features.

Stark ladder peaks are influenced by continuum state coupling.

Calculated spectra align well with experimental data.

Abstract

A new, exact method for calculating excitonic absorption in superlattices is described. It is used to obtain high resolution spectra showing the saddle point exciton feature near the top of the miniband. The evolution of this feature is followed through a series of structures with increasing miniband width. The Stark ladder of peaks produced by an axial electric field is investigated, and it is shown that for weak fields the line shapes are strongly modified by coupling to continuum states, taking the form of Fano resonances. The calculated spectra, when suitably broadened, are found to be in good agreement with experimental results.