Scanning gate microscopy of ultra clean carbon nanotube quantum dots

TL;DR

This study uses scanning gate microscopy to investigate ultra clean carbon nanotube quantum dots, revealing electrostatic screening effects and tunable interactions between double quantum dots, advancing understanding of their electrostatic properties.

Contribution

First demonstration of electrostatic screening effects and tunable inter-dot interactions in ultra clean carbon nanotube quantum dots using scanning gate microscopy.

Findings

Electrostatic screening creates multiple Coulomb ring sets.

Quantum dot interactions can be tuned from weak to strong coupling.

High-resolution visualization of quantum dot electrostatics.

Abstract

We perform scanning gate microscopy on individual suspended carbon nanotube quantum dots. The size and position of the quantum dots can be visually identified from the concentric high conductance rings. For the ultra clean devices used in this study, two new effects are clearly identified. Electrostatic screening creates non-overlapping multiple sets of Coulomb rings from a single quantum dot. In double quantum dots, by changing the tip voltage, the interactions between the quantum dots can be tuned from the weak to strong coupling regime.