Two-Electron Linear Intersubband Light Absorption in a Biased Quantum Well

TL;DR

This paper reveals a new many-body correlation effect in quantum wells, showing a second absorption peak at double the frequency caused by electron-electron interactions, enabling insights into intersubband plasmon dispersion.

Contribution

It introduces the discovery of a second absorption peak due to two-electron excitations, highlighting a novel many-body correlation effect in quantum well optical response.

Findings

Existence of a second absorption peak at double the intersubband frequency.

The peak is caused by electron-electron interactions and two-electron excitations.

The peak shape includes a sharp two-plasmon feature and a broader two-particle band.

Abstract

We point out a novel manifestation of many-body correlations in the linear optical response of electrons confined in a quantum well. Namely, we demonstrate that along with conventional absorption peak at frequency close to intersubband energy, there exists an additional peak at double frequency. This new peak is solely due to electron-electron interactions, and can be understood as excitation of two electrons by a single photon. The actual peak lineshape is comprised of a sharp feature, due to excitation of pairs of intersubband plasmons, on top of a broader band due to absorption by two single-particle excitations. The two-plasmon contribution allows to infer intersubband plasmon dispersion from linear absorption experiments.