Finite-thickness effects in ground-state transitions of two-electron quantum dots

TL;DR

This paper investigates how the finite vertical thickness of two-electron quantum dots affects their ground-state transitions, providing a more accurate model that aligns with experimental observations and reveals the conditions for Wigner molecule formation.

Contribution

It introduces a three-dimensional model accounting for quantum dot thickness, explaining experimental results and predicting the persistence of singlet-triplet transitions.

Findings

Second singlet-triplet transition vanishes with increased vertical extension in 3D.

Slight reduction in lateral confinement leads to Wigner molecule formation.

3D model aligns well with experimental data.

Abstract

Using the exactly solvable excitation spectrum of two-electron quantum dots with parabolic potential, we show that the inclusion of the vertical extension of the quantum dot provides a consistent description of the experimental findings of Nishi et al. [Phys.Rev.B75, 121301(R) (2007)]. We found that the second singlet-triplet transition in the ground state is a vanishing function of the lateral confinement in the three-dimensional case, while it always persists in the two-dimensional case. We show that a slight decrease of the lateral confinement leads to a formation of the Wigner molecule at low magnetic fields.