Singlet-triplet transition in double quantum dots in two-dimensional topological insulators

TL;DR

This paper investigates how the ground state of two electrons in coupled quantum dots within a 2D topological insulator can transition between singlet and triplet states by tuning system parameters, influenced by pseudospin effects.

Contribution

It reveals the conditions under which a singlet-triplet transition occurs in double quantum dots in 2D topological insulators, highlighting the role of pseudospin components.

Findings

Ground state can be triplet-like or singlet depending on system parameters.

Transition between states can be controlled by adjusting quantum dot potentials.

Pseudospin components significantly affect Coulomb and exchange energies.

Abstract

We study two-electron states confined in two coupled quantum dots formed by a short-range potential in a two-dimensional topological insulator. It is shown that there is a fairly wide range of the system parameters, where the ground state is a tripletlike state formed by a superposition of two spin-polarized states. Outside this range, the ground state is a singlet. A transition between the singlet and triplet states can be realized by changing the potential of the quantum dots. The effect is caused by a significant change in the energies of the Coulomb repulsion and the exchange interaction of electrons due to the presence of the pseudospin components of the wave function when the band spectrum is inverted.