| One-dimensional electron systems have been predicted to be fundamentally different from those in higher dimensions, particularly with respect to the way in which interactions are screened. While theoretical work on these systems dates back to the 1950s, it has only been since 1990 that the fabrication and investigation of truly one-dimensional systems on the nanometer scale have been made possible by advances in chemistry and molecular beam epitaxy.; This dissertation reports transport measurements on three systems---carbon nanotubes, carbon nanotube peapods and 'cleaved edge overgrowth' GaAs hole wires - each of which enables the investigation of a different aspect of one-dimensional physics.; The main part of this work focuses on peapod measurements, for which the main results are as follows. (1) We found, rather unexpectedly, that the periodically intercalated C_60 molecules do not significantly modify the nanotube's electonic structure near the Fermi level. (2) We were able to carefully study in these devices the evolution of the spin-1/2 Kondo effect in a magnetic field, on which there has been some theoretical controversy. We find that existing theories agree with the experimental data qualitatively but not in their details. (3) We observed an underscreened spin-1 Kondo effect. Performing the first tuning of the transition between singlet and triplet ground states independently with a gate voltage and magnetic field, we find that for the most part our data are explained by a simple model; however, some puzzles remain.; Ballistic transport in the first CEO hole quantum wires in GaAs was also measured. Basic characterisation of these wires at finite bias and two different directions of magnetic field reveal an anisotropic g factor likely due to the combined effects of spin-orbit coupling and confinement. With magnetic field parallel to the wire we also observe what we believe to be direct evidence for a spin-orbit induced gap in the spectrum of the wire. The analysis of these data is ongoing.; Finally, some measurements on nanotubes are presented. |
