Wave-vector dependence of spin and density multipole excitations in quantum dots

TL;DR

This study uses time-dependent density functional theory to analyze how wave-vector influences spin and charge excitations in quantum dots, confirming experimental observations and identifying mode angular momentum.

Contribution

It provides the first detailed wave-vector dependence analysis of multipole excitations in quantum dots using TDDFT, aligning theory with experimental Raman data.

Findings

Excitation energies are wave-vector independent.

Excitation intensities vary with wave-vector.

Theoretical results match experimental mode energies and angular momentum assignments.

Abstract

We have employed time-dependent local-spin density functional theory to analyze the multipole spin and charge density excitations in GaAs-AlGaAs quantum dots. The on-plane transferred momentum degree of freedom has been taken into account, and the wave-vector dependence of the excitations is discussed. In agreement with previous experiments, we have found that the energies of these modes do not depend on the transferred wave-vector, although their intensities do. Comparison with a recent resonant Raman scattering experiment [C. Sch\"uller et al, Phys. Rev. Lett {\bf 80}, 2673 (1998)] is made. This allows to identify the angular momentum of several of the observed modes as well as to reproduce their energies.