Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.21: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Multi-level Kondo effect in single-wall carbon nanotubes (SWNT) — •Theresa Hecht, Michael Sindel und Jan von Delft — Department of Physics and Center for NanoScience, LMU München, Theresienstr. 37, 80333 München

Recently Herrero et al. investigated the Kondo effect [1] in SWNTs. In absence of a magnetic field an (approximate) orbital as well as a spin degeneracy is present in those SWNT. Herrero et al. were able to identify two consequences of this degeneracy, namely the so-called SU(4) Kondo effect [2] and a purely orbital Kondo effect [3]. A finite magnetic field was found to remove both spin and orbital degeneracy, reflected by multiple splittings of the Kondo resonance. Moreover, a particular magnetic field might even result in a degeneracy between adjacent orbital levels, giving rise to a purely orbital Kondo effect [3]. In some samples, the Kondo resonance is split even in the complete absence of a magnetic field, suggesting that the orbital states are weakly coupled, lifting their degeneracy.

Motivated by these experiments, we study a two-level Anderson model by means of Wilson’s numerical renormalization group method. We investigate both magnetic field and energy dependence of the spectral function and propose a mechanism that leads to the various types of splittings of the Kondo resonance.
P. Jarillo-Herrero et al., submitted to Nature
L. Borda et al., PRL 90, 026602, (2003)
P. Jarillo-Herrero et al., to be published