Zero-field splitting of Kondo resonances in a carbon nanotube quantum dot

J. Nygard, W. F. Koehl, N. Mason, L. DiCarlo, C. M. Marcus

Published 2004-10-19, updated 2004-10-25Version 2

We present low-temperature electron transport measurements on a single-wall carbon nanotube quantum dot exhibiting Kondo resonances at low temperature. Contrary to the usual behavior for the spin-1/2 Kondo effect we find that the temperature dependence of the zero bias conductance is nonmonotonic. In nonlinear transport measurements low-energy splittings of the Kondo resonances are observed at zero magnetic field. We suggest that these anomalies reflect interactions between the nanotube and a magnetic (catalyst) particle. The nanotube device may effectively act as a ferromagnetically contacted Kondo dot.