Kondo effect in a carbon nanotube with spin-orbit interaction and valley mixing: A DM-NRG study

Abstract

We investigate the effects of spin-orbit interaction (SOI) and valley mixing on the transport and dynamical properties of a carbon nanotube (CNT) quantum dot in the Kondo regime. As these perturbations break the pseudo-spin symmetry in the CNT spectrum but preserve time-reversal symmetry, they induce a finite splitting $\Delta$ between formerly degenerate Kramers pairs. Correspondingly, a crossover from the SU(4) to the SU(2)-Kondo effect occurs as the strength of these symmetry breaking parameters is varied. Clear signatures of the crossover are discussed both at the level of the spectral function as well as of the conductance. In particular, we demonstrate numerically and support with scaling arguments, that the Kondo temperature scales inversely with the splitting $\Delta$ in the crossover regime. In presence of a finite magnetic field, time reversal symmetry is also broken. We investigate the effects of both parallel and perpendicular fields (with respect to the tube's axis), and discuss the conditions under which Kondo revivals may be achieved.

13 pages, 17 figures

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• Field-Enhanced Kondo Correlations in a Half-Filling Nanotube Dot: Evolution of an SU(N) Fermi-Liquid Fixed Point
• Nonlinear Fermi-liquid transport through a quantum dot in asymmetric tunnel junctions
• Intra- and inter-shell Kondo effects in carbon nanotube quantum dots
• Role of bias and tunneling asymmetries in nonlinear Fermi-liquid transport through an SU($N$) quantum dot
• Thermoelectric transport and current noise through a multilevel Anderson impurity: Three-body Fermi-liquid corrections in quantum dots and magnetic alloys
• The PointGroupNRG code for numerical renormalization group calculations with discrete point-group symmetries
• Electron-phonon interaction and electronic correlations in transport through electrostatically and tunnel coupled quantum dots
• Unhiding a concealed resonance by multiple Kondo transitions in a quantum dot
• Three-body Fermi liquid corrections for an infinite-$U$ SU($N$) Anderson impurity model
• Fractional shot noise of an SU(N) Kondo system