Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 29: Nanotubes and Nanoribbons

TT 29.2: Hauptvortrag

Dienstag, 2. April 2019, 14:30–15:00, H2

Nanomechanical characterization of the Kondo charge dynamics in a carbon nanotube — Karl J. G. Götz, Daniel R. Schmid, Felix J. Schupp, Peter L. Stiller, Christoph Strunk, and •Andreas K. Hüttel — Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany

Suspended single wall carbon nanotubes are at cryogenic temperatures both extraordinary nanomechanical systems and prototypical clean and defect-free single electron devices. This allows for many interesting studies. In particular, by measuring the gate voltage dependence of the transversal vibration frequency, the evolution of the charge on a quantum dot embedded in the nanotube can be precisely evaluated.

We apply this technique to the case of strong Kondo correlations between a quantum dot and its contacts. The current through the nanotube displays a clear odd-even pattern, with a zero-bias conductance anomaly at odd electron number. The time-averaged charge on the quantum dot, however, shows no odd-even pattern, and can be well modelled via sequential tunneling only. We conclude that the Kondo current is carried via virtual occupation of the quantum dot alone.

In addition, the simultaneous detection of charge and current signal allows us to compare the gate potentials where on one hand the current is maximal and on the other hand the charge in the quantum dot increases. Here, a distinct relative shift is observed, decreasing logarithmically with temperature. Our observations agree very well with models for Kondo-correlated quantum dots.
K. J. G. Götz et al., PRL 120, 246802 (2018)