Dresden 2014 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 73: Transport: Carbon Nanotubes (organized by TT)
TT 73.8: Vortrag
Mittwoch, 2. April 2014, 18:15–18:30, HSZ 304
Theory of the Kondo effect in carbon nanotube quantum dots with broken SU(4) symmetry — •Sergey Smirnov1, Magdalena Margańska1, Daniel R. Schmid2, Alois Dirnaichner2, Peter L. Stiller2, Andreas K. Hüttel2, Christoph Strunk2, and Milena Grifoni1 — 1Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany — 2Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
We develop an effective low energy field theory for the Kondo effect in a quantum dot where the original four-fold degeneracy of the dot level is partially removed. The SU(2) Keldysh effective action approach [1,2] is generalized to the case of the broken SU(4) Anderson model with spin and orbital degrees of freedom. The theory is valid in the strong and weak coupling regimes as well as in the crossover. It provides universal differential conductance with the scale having the correct limiting behavior for the SU(2) and SU(4) cases. As an application to a physical system, we explore the Kondo effect in a quantum dot made of a carbon nanotube with strong spin-orbit interaction and valley mixing. The symmetry properties of the carbon nanotube Hamiltonian are exploited to identify the structure of the Keldysh effective action. We further investigate in detail the Kondo resonance and its behavior in perpendicular and parallel magnetic fields and compare it with recent experiments on the Kondo effect in ultraclean carbon nanotubes.
S. Smirnov and M. Grifoni, Phys. Rev. B 87, 121302(R) (2013).
S. Smirnov and M. Grifoni, New. J. Phys. 15, 073047 (2013).