Kasper Grove-Rasmussen

Learn More
We fabricated reproducible high transparency superconducting contacts consisting of superconducting Ti/Al/Ti trilayers to gated single-wall carbon nanotubes. The reported semiconducting single-wall carbon nanotubes have normal state differential conductance up to 3e2/h and exhibit clear Fabry-Perot interference patterns in the bias spectroscopy plot. We(More)
High quality single wall carbon nanotube quantum dots have been made showing both metallic and semiconducting behavior. Some of the devices are identified as small band gap semiconducting nanotubes with relatively high broad conductance oscillations for hole transport through the valence band and low conductance Coulomb blockade oscillations for electron(More)
We here present additional theoretical analysis and experimental data supporting the conclusions in the article. First, the carbon nanotube dispersion relation including spin-orbit interaction is reviewed starting from a modified Dirac Hamiltonian, and the single-particle model used in the fitting procedure is explained. Second, tunneling spectroscopy data(More)
A top-gated single-wall carbon nanotube is used to define three coupled quantum dots in series between two electrodes. The additional electron number on each quantum dot is controlled by top-gate voltages allowing for current measurements of single, double, and triple quantum dot stability diagrams. Simulations using a capacitor model including tunnel(More)
We report on quantum dot based Josephson junctions designed specifically for measuring the supercurrent. From high-accuracy fitting of the current-voltage characteristics, we determine the full magnitude of the supercurrent (critical current). Strong gate modulation of the critical current is observed through several consecutive Coulomb blockade(More)
We report measurements of the nonlinear conductance of InAs nanowire quantum dots coupled to superconducting leads. We observe a clear alternation between odd and even occupation of the dot, with subgap peaks at |V(sd)| = Delta/e markedly stronger (weaker) than the quasiparticle tunneling peaks at |V(sd)| = 2Delta/e for odd (even) occupation. We attribute(More)
An artificial two-atomic molecule, also called a double quantum dot (DQD), is an ideal system for exploring few-electron physics. Interactions between just two electrons have been explored in such systems using the singlet and triplet states as the two states in a quantum two-level system. An alternative and attractive material for studying spin-based(More)
We have studied tunneling of electrons into multiwall carbon nanotubes (NTs) in NT-gold and NT-NT junctions, the latter created by atomic force microscope manipulation. The tunneling conductance goes to zero as the energy (temperature and bias) is reduced, and the functional form is consistent with a power law. The exponents depend upon sample geometry. The(More)
We investigate how the orbital magnetic moments of electron and hole states in a carbon nanotube quantum dot depend on the number of carriers on the dot. Low temperature transport measurements are carried out in a setup where the device can be rotated in an applied magnetic field, thus enabling accurate alignment with the nanotube axis. The field dependence(More)
By means of sequential and cotunneling spectroscopy, we study the tunnel couplings between metallic leads and individual levels in a carbon nanotube quantum dot. The levels are ordered in shells consisting of two doublets with strong- and weak-tunnel couplings, leading to gate-dependent level renormalization. By comparison to a one- and two-shell model,(More)