Gate controlled coupling of intersubband plasmons

TL;DR

This paper investigates how Coulomb interactions couple intersubband plasmons in a doped quantum well, demonstrating tunable optical absorption spectra influenced by electronic density and gate voltage.

Contribution

It reveals that intersubband transitions in quantum wells are coupled via Coulomb interaction, affecting their optical response and tunability, which was not previously characterized.

Findings

Coulomb coupling strongly renormalizes absorption amplitudes

Optical spectra depend on electronic density and gate voltage

Coupled oscillator model accurately describes the system

Abstract

The optical response of a heavily doped quantum well, with two occupied subbands, has been investigated as a function of the electronic density. It is shown that the two optically active transitions are mutually coupled by dipole-dipole Coulomb interaction, which strongly renormalizes their absorption amplitude. In order to demonstrate this effect, we have measured a set of optical spectra on a device in which the electronic density can be tuned by the application of a gate voltage. Our results show that the absorption spectra can be correctly described only by taking into account the Coulomb coupling between the two transitions. As a consequence, the optical dipoles originating from intersubband transitions are not independent, but rather coupled oscillators with an adjustable strength.