Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 45: Nano- and Optomechanics

TT 45.1: Talk

Tuesday, March 13, 2018, 11:45–12:00, H 0110

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, 93053 Regensburg, Germany

Suspended single wall carbon nanotubes are at cryogenic temperatures both extraordinary nanomechanical systems and clean and defect-free single electron devices. 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 evaluated.

We apply this technique to the limit of strong Kondo correlations between a nanotube 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 charge on the quantum dot, however, shows no such odd-even pattern, and can be well modeled via sequential tunneling only. We conclude that the Kondo current is carried via virtual occupation of the quantum dot alone, without impact on the vibration. This is in excellent agreement with recent results coupling a nanotube to a coplanar waveguide resonator.

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, which decreases logarithmically with temperature, displaying the typical scaling of the Kondo effect.