Kondo effects in small-bandgap carbon nanotube quantum dots

Abstract

We study the magnetoconductance of small-bandgap carbon nanotube quantum dots in the presence of spin–orbit coupling in the strong-correlations regime. A finite-U slave-boson mean-field approach is used to study many-body effects. Different degeneracies are restored in a magnetic field and Kondo effects of different symmetries arise, including SU(3) effects of different types. Full spin–orbital degeneracy might be recovered at zero field and, correspondingly, the SU(4) Kondo effect sets in. We point out the possibility of the occurrence of electron–hole Kondo effects in slanting magnetic fields, which we predict to occur in magnetic fields with an orientation close to perpendicular. When the field approaches a transverse orientation a crossover from SU(2) or SU(3) symmetry into SU(4) is observed.

Intra- and inter-shell Kondo effects in carbon nanotube quantum dots

“…To get more comprehensive description of intra-and intershell many-body effects on equal footing extended basis of states from both shells have to be considered requiring a use of more slave boson operators. This problem will be discussed elsewhere [78]. Also the presented discussion of SU(3) Kondo effect is only preliminarily, the more detailed analysis is under our investigation.…”