Excited state spectroscopy in carbon nanotube double quantum dots

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 and control the coupling between them, and we observe 4-fold shell filling. We perform inelastic transport spectroscopy via the excited states in the double quantum dot, a necessary step toward the implementation of new microwave-based experiments.