Impact of competing energy scales on the shell-filling sequence in elliptic bilayer graphene quantum dots

TL;DR

This study investigates how competing energy scales, including electron interactions and valley g-factors, influence the shell-filling sequence in elliptic bilayer graphene quantum dots, revealing size-dependent effects and complex electrostatics.

Contribution

It demonstrates the necessity of including both short-range electron interactions and wavefunction-dependent valley g-factors to accurately describe shell-filling in bilayer graphene quantum dots.

Findings

Valley g-factor and electron-electron interaction energy splittings increase as QD size decreases.

Shell-filling sequence is affected by both short-range interactions and valley g-factors.

Electrostatic charging energy does not scale simply with QD size, indicating complex electrostatics.

Abstract

We report on a detailed investigation of the shell-filling sequence in electrostatically defined elliptic bilayer graphene quantum dots (QDs) in the regime of low charge carrier occupation, $N \leq 12$, by means of magnetotransport spectroscopy and numerical calculations. We show the necessity of including both short-range electron-electron interaction and wavefunction-dependent valley g-factors for understanding the overall fourfold shell-filling sequence. These factors lead to an additional energy splitting at half-filling of each orbital state and different energy shifts in out-of-plane magnetic fields. Analysis of 31 different BLG QDs reveals that both valley g-factor and electron-electron interaction induced energy splitting increase with decreasing QD size, validating theory. However, we find that the electrostatic charging energy of such gate-defined QDs does not correlate consistently with their size, indicating complex electrostatics. These findings offer significant insights for future BLG QD devices and circuit designs.