Transport Spectroscopy of Single-Walled Carbon Nanotubes

We have performed transport spectroscopy on individual ropes of single-walled carbon nanotubes. We find that the levels are Zeeman split in a magnetic field, with a g-factor of 2.04 +- 0.05. The observed pattern of peak splittings indicates the parity of the number of electrons on the dot. In one device there are also signs of the presence of a second dot. We observe features which resemble anticrossings between quantum levels in the two dots, which may be formed from separate conducting nanotubes within the rope.