Engineering Exchange Coupling in Double Elliptic Quantum Dots

TL;DR

This study models elliptic quantum dots with varying aspect ratios and magnetic fields to analyze how their exchange energy and charge stability are affected, revealing key dependencies on confinement and detuning.

Contribution

It introduces a numerical exact diagonalization approach to analyze exchange coupling in asymmetric elliptic quantum dots with magnetic fields.

Findings

Exchange energy increases with confinement ratio at zero magnetic field.

Magnetic field for singlet-triplet transition decreases with increased confinement asymmetry.

Exchange energy shows superlinear increase with inter-dot detuning before saturation.

Abstract

Coupled elliptic quantum dots with different aspect ratios containing up to two electrons are studied using a model confinement potential in the presence of magnetic fields. Single and two particle Schroedinger equations are solved using numerical exact diagonolization to obtain the exchange energy and chemical potentials. As the ratio between the confinement strengths in directions perpendicular and parallel to the coupling direction of the double dots increases, the exchange energy at zero magnetic field increases, while the magnetic field of the singlet-triplet transition decreases. By investigating the charge stability diagram, we find that as inter-dot detuning increases, the absolute value of the exchange energy increases superlinearly followed by saturation. This behavior is attributed to the electron density differences between the singlet and triplet states in the assymetric quantum dot systems.