Broadband THz study of excitonic resonances in the high-density regime

TL;DR

This study uses terahertz spectroscopy to investigate how high-density excitonic populations in GaAs/AlGaAs quantum wells affect intra-excitonic transitions, revealing significant shifts and broadening with increasing excitation density.

Contribution

First terahertz measurement of intra-excitonic 1s-2p transition at high densities in quantum wells, providing quantitative analysis of exciton and electron-hole pair dynamics.

Findings

Resonance shifts and broadens with increasing density

Disappearance of the intra-excitonic resonance at high densities

Enhanced energy shift compared to near-infrared absorption

Abstract

We report the first terahertz study of the intra-excitonic 1s-2p transition at high excitation densities in GaAs/AlGaAs quantum wells. A strong shift, broadening, and ultimately the disappearance of this resonance occurs with increasing density, after ultrafast photoexcitation at the near-infrared exciton line. Densities of excitons and unbound electron-hole pairs are followed quantitatively using a model of the composite terahertz dielectric response. Comparison with near-infrared absorption changes reveals a significantly enhanced energy shift and broadening of the intra-excitonic resonance.