Key points are not available for this paper at this time.
We study the SU(4) Kondo effect in carbon nanotube quantum dots, where doubly degenerate orbitals form four-electron ``shells.'' The SU(4) Kondo behavior is investigated for one, two, and three electrons in the topmost shell. While the Kondo state of two electrons is quenched by a magnetic field, in the case of an odd number of electrons two types of SU(2) Kondo effect may survive. Namely, the spin SU(2) state is realized in a magnetic field parallel to the nanotube (inducing primarily orbital splitting). Application of the perpendicular field (inducing Zeeman splitting) results in the orbital SU(2) Kondo effect.
Makarovski et al. (Mon,) studied this question.