# Dresden 2014 – wissenschaftliches Programm

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# HL: Fachverband Halbleiterphysik

## HL 80: Transport: Carbon nanotubes (organized by TT)

### HL 80.7: Vortrag

### Mittwoch, 2. April 2014, 18:00–18:15, HSZ 304

**Fine structure of the Kondo resonance in carbon nanotube quantum dots** — Daniel R. Schmid^{1}, Sergey Smirnov^{2}, Magdalena Margańska^{2}, Alois Dirnaichner^{1}, Peter L. Stiller^{1}, Milena Grifoni^{2}, •Andreas K. Hüttel^{1}, and Christoph Strunk^{1} — ^{1}Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany — ^{2}Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany

Ultraclean carbon nanotubes enable spectroscopy of the unperturbed quantum mechanical properties of electronic states in transport experiments with a high degree of precision. This applies to the case of opaque tunnel barriers between nanotube and leads and, e.g., the excitation spectrum of one or two electrons trapped in the quantum dot as well as to the case of many electrons and strong coupling to the leads.

Manybody correlations in carbon nanotubes with a quadruplet of both spin and valley (K-K’) degenerate quantum states can give rise to the so-called SU(4) Kondo effect. We demonstrate a highly regular carbon nanotube quantum dot, where SU(4) symmetry is broken by intrinsic both spin-orbit interaction and valley mixing. This leads to a characteristic Kondo peak in differential conductance at zero bias along with satellite peaks at finite bias. The evolution of these peaks is strikingly different at finite perpendicular and parallel magnetic fields. We demonstrate how their combined spin and orbital origin and their evolution at finite magnetic fields can be understood in detail in terms of the discrete symmetries of the carbon nanotube Hamiltonian.