Raman Scattering Spectra of Elementary Electronic Excitations in Coupled Double-Quantum Well Structures

TL;DR

This paper uses a self-consistent linear response theory to calculate elementary excitations and Raman spectra in coupled double-quantum well structures, comparing theoretical results with experimental data.

Contribution

It provides a theoretical analysis of inelastic light-scattering spectra in coupled quantum wells using TDLDA, highlighting agreement and discrepancies with experiments.

Findings

Intersubband spin density excitations merge with single particle excitations as Fermi energy increases.

The excitonic shift decreases monotonically with increasing Fermi energy.

The calculation does not reproduce the experimentally observed abrupt suppression of the excitonic shift.

Abstract

Using the time-dependent-local-density-approximation (TDLDA) within a self-consistent linear response theory, we calculate the elementary excitation energies and the associated inelastic light-scattering spectra of a strongly coupled two-component plasma in a double-quantum well system with electron occupation of symmetric and antisymmetric subbands. We find, consistent with the results of a recent experimental Raman scattering study, that the intersubband spin density excitations tend to merge with the single particle excitations (i.e. the excitonic shift decreases monotonically) as the Fermi energy increases beyond the symmetric-antisymmetric energy gap $\bigtriangleup_{SAS}$. However, our TDLDA calculation does not show the abrupt suppresion of the excitonic shift seen experimentally at a finite value of the subband occupancy parameter $\eta \equiv \bigtriangleup_{\text{SAS}} / E_{\text{F}}$.