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TT: Fachverband Tiefe Temperaturen

TT 8: Correlated Electrons: Quantum Impurities, Kondo Physics

TT 8.6: Vortrag

Montag, 7. März 2016, 11:45–12:00, H21

Kondo effect in a carbon nanotube with spin-orbit interaction and valley mixing: A DM-NRG study — •Davide Mantelli¹, Catalin Pascu Moca^2,3, Gergely Zarand², and Milena Grifoni¹ — ¹Iunstitut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Deutschland — ²Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, HU-1521 Budapest, Hungary — ³Department of Physics, University of Oradea, 410087 Oradea, Romania

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 Δ 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 Δ 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.