Excitation spectra of two correlated electrons in a quantum dot

TL;DR

This paper reports experimental and theoretical analysis of the excitation spectrum of a two-electron quantum dot, highlighting the importance of electron correlations and comparing different theoretical approaches.

Contribution

It provides the first detailed experimental measurements of excited states in a two-electron quantum dot and compares various theoretical models to interpret these states.

Findings

Excited states beyond the lowest singlet and triplet are observed.

Exact diagonalization reproduces the experimental spectra well.

The generalized Heitler-London approach effectively accounts for electron correlations.

Abstract

Measurements and a theoretical interpretation of the excitation spectrum of a two-electron quantum dot fabricated on a parabolic Ga[Al]As quantum well are reported. Experimentally, excited states are found beyond the well-known lowest singlet- and triplet states. These states can be reproduced in an exact diagonalization calculation of a parabolic dot with moderate in-plane anisotropy. The calculated spectra are in reasonable quantitative agreement with the measurement, and suggest that correlations between the electrons play a significant role in this system. Comparison of the exact results with the restricted Hartree-Fock and the generalized Heitler-London approach shows that the latter is more appropriate for this system because it can account for the spatial correlation of the electron states.