Single-electron shell occupation and effective $g$-factor in few-electron nanowire quantum dots

TL;DR

This study investigates the energy level structure and effective $g$-factor differences in few-electron nanowire quantum dots, revealing how electron number and dot asymmetry influence spin properties and spectra.

Contribution

It provides a numerically exact analysis of energy levels and $g$-factor differences in few-electron quantum dots, highlighting effects of electron number and dot length asymmetry.

Findings

Effective $g$-factor differences depend on dot length and electron number.

Increased electron number amplifies $g$-factor differences even in symmetric dots.

Most electrons form a frozen singlet core, simplifying the system's description.

Abstract

Nanowire double quantum dots occupied by an even number of electrons are investigated in the context of energy level structure revealed by electric dipole spin resonance measurements. We use numerically exact configuration interaction approach up to 6 electrons for systems tuned to Pauli spin blockade regime. We point out the differences between the spectra of systems with two and a greater number of electrons. For two-electrons the unequal length of the dots results in a different effective $g$-factors in the dots as observed by the recent experiments. For an increased number of electrons the $g$-factor difference between the dots appears already for symmetric systems and it is greatly amplified when the dots are of unequal length. We find that in the lowest energy states all except of two electrons form a frozen core of singlet shells that can be separated away for description of the properties of the system.