Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 26: Focus Session: Engineered Magnetic Impurities: Interaction and Superconductivity

TT 26.3: Hauptvortrag

Dienstag, 8. März 2016, 10:30–11:00, H20

Engineering the Kondo Effect in clean Carbon Nanotubes — •Christoph Strunk — Inst. f. Experimental and Applied Physics, University of Regensburg

Ultraclean carbon nanotubes (CNTs) form quantum dots of well-defined atomic structure at low temperatures. Transport spectroscopy of ground and excited states as a function of electron numbers in a parallel magnetic field results in detailed information about the band structures, in particular on spin-orbit and KK’-mixing effects.

This information is exploited in the analysis of the SU(4) Kondo effect [1] occurring at larger electron numbers, where the devices become more transmissive. The slightly broken fourfold degeneracy in our device gives rise to satellites of the Kondo peak that shift in a characteristic way in perpendicular and parallel magnetic field. Our observations reflect discrete symmetries of the CNT Hamiltionian, and are well reproduced by state of the art theoretical modeling [2].

On the other hand, multichannel electron interference is observed on the hole side of the CNT spectrum, where Coulomb effects are suppressed. A secondary interference effect is observed that provides information about the chiral angle of the CNTs by virtue of the trigonal warping of the underlying graphene band structure.
P. Jarillo-Herrero et al., Nature 434, 484 (2005)
S. Smirnov and M. Grifoni, Phys. Rev. B 87, 121302 (2013)