Coupling of bonding and antibonding electron orbitals in double quantum dots by spin-orbit interaction

TL;DR

This study systematically analyzes how spin-orbit interaction couples bonding and antibonding orbitals in double quantum dots, affecting electronic states and optical transitions, with implications for quantum dot-based optoelectronic devices.

Contribution

It provides a detailed exact diagonalization analysis of spin-orbit effects on few-electron states, revealing new coupling mechanisms and optical transition behaviors in double quantum dots.

Findings

Spin-orbit coupling induces coupling between bonding and antibonding orbitals.

Optical transition energies can be increased by in-plane electric fields for odd electron numbers.

Spin-orbit interaction enables low-energy optical transitions forbidden without it.

Abstract

We perform a systematic exact diagonalization study of spin-orbit coupling effects for stationary few-electron states confined in quasi two-dimensional double quantum dots. We describe the spin-orbit-interaction induced coupling between bonding and antibonding orbitals and its consequences for magneto-optical absorption spectrum. The spin-orbit coupling for odd electron numbers (one, three) %only weakly perturbs the ground-state wave functions. %Nevertheless, %the spin-orbit interaction opens avoided crossings between low energy excited levels of opposite spin orientation and opposite spatial parity. For two-electrons the spin-orbit coupling allows for low-energy optical transitions that are otherwise forbidden by spin and parity selection rules. We demonstrate that the energies of optical transitions can be significantly increased by an in-plane electric field but only for odd electron numbers. Occupation of single-electron orbitals and effects of spin-orbit coupling on electron distribution between the dots are also discussed.