title: Tunable few-electron double quantum dots and Klein tunnelling in ultraclean carbon nanotubes.
abstract: Quantum dots defined in carbon nanotubes are a platform for both basic scientific studies and research into new device applications. In particular, they have unique properties that make them attractive for studying the coherent properties of single-electron spins. To perform such experiments it is necessary to confine a single electron in a quantum dot with highly tunable barriers, but disorder has prevented tunable nanotube-based quantum-dot devices from reaching the single-electron regime. Here, we use local gate voltages applied to an ultraclean suspended nanotube to confine a single electron in both a single quantum dot and, for the first time, in a tunable double quantum dot. This tunability is limited by a novel type of tunnelling that is analogous to the tunnelling in the Klein paradox of relativistic quantum mechanics.
authors.affiliation: Kavli Institute of NanoScience, Delft University of Technology, Delft, The Netherlands. G.A.Steele@tudelft.nl
authors.forename: G A
authors.initials: GA
authors.lastname: Steele
authors.forename: G
authors.initials: G
authors.lastname: Gotz
authors.forename: L P
authors.initials: LP
authors.lastname: Kouwenhoven