Theoretical study of phonon-assisted singlet-singlet relaxation in two-electron semiconductor quantum dot molecules

TL;DR

This theoretical study investigates phonon-assisted singlet-singlet relaxation in two-electron semiconductor quantum dot molecules, highlighting the dominant role of piezoelectric coupling and the impact of system parameters on relaxation rates.

Contribution

The paper provides a detailed theoretical analysis of phonon-assisted relaxation mechanisms, emphasizing the significance of piezoelectric effects and parameter dependencies in quantum dot molecules.

Findings

Piezoelectric coupling dominates relaxation in certain parameter ranges.

Relaxation rates can reach up to 160 ns$^{-1}$ at zero temperature.

Coulomb interaction influences relaxation dynamics.

Abstract

Phonon-assisted singlet-singlet relaxation in semiconductor quantum dot molecules is studied theoretically. Laterally coupled quantum dot structures doped with two electrons are considered. We take into account interaction with acoustic phonon modes via deformation potential and piezoelectric coupling. We show that piezoelectric mechanism for the considered system is of great importance and for some ranges of quantum dot molecule parameters is the dominant contribution to relaxation. It is shown that the phonon-assisted tunneling rates reach much higher values (up to 160 ns$^{-1}$ even at zero temperature) in comparison with other decoherence processes like spin-orbit coupling ($\sim$ 0.01 ns$^{-1}$). The influence of Coulomb interaction is discussed and its consequences are indicated. We calculate the relaxation rates for GaAs quantum dot molecules and study the dependence on quantum dot size, distance and offset between the constituent quantum dots. In addition the temperature dependence of the tunneling rates is analyzed.