Excited state spectroscopy in carbon nanotube double quantum dots

TL;DR

This paper presents low-temperature spectroscopy of a tunable carbon nanotube double quantum dot, utilizing a novel fabrication method for top-gates that enables detailed excited state analysis crucial for future microwave experiments.

Contribution

Introduces a new top-gate fabrication technique for carbon nanotube quantum dots, enabling precise control and excited state spectroscopy.

Findings

Observation of four-fold shell filling.

Successful inelastic transport spectroscopy of excited states.

Enhanced control over quantum dot coupling.

Abstract

We report on low temperature measurements in a fully tunable carbon nanotube double quantum dot. A new fabrication technique has been used for the top-gates in order to avoid covering the whole nanotube with an oxide layer as in previous experiments. The top-gates allow us to form single dots, control the coupling between them and we observe four-fold shell filling. We perform inelastic transport spectroscopy via the excited states in the double quantum dot, a necessary step towards the implementation of new microwave-based experiments.