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TT: Fachverband Tiefe Temperaturen

TT 75: Poster Session: Transport 1

TT 75.25: Poster

Donnerstag, 23. März 2017, 15:00–19:00, P2-EG

Magnetic field control of the electron-vibron coupling in a carbon nanotube quantum dot — Peter L. Stiller, Daniel R. Schmid, Christoph Strunk, and •Andreas K. Hüttel — Institute for Experimental and Applied Physics, Universität Regensburg, Regensburg, Germany

Quantum dots defined in suspended single wall carbon nanotubes define a prototypical nano-electromechanical system: the quantized harmonic oscillator behaviour of the longitudinal vibration mode becomes clearly visible in low-temperature transport spectroscopy.

Here, we present measurements on a nanotube device tuned to the region of 0 ≤ N ≤ 2 trapped electrons, i.e., close to the electronic band gap. A highly localized electronic system in strong Coulomb blockade is present. At finite bias, we demonstrate the emergence of Franck-Condon sidebands in single electron tunneling, corresponding to the longitudinal vibration, solely in a magnetic field along the carbon nanotube axis.

The magnetic field evolution of the Franck-Condon coupling factor g is analyzed. For the two-electron ground state it increases from g=0 starting at B≃ 1.5 T and saturates around B≃ 3.3 T, however, for different electronic quantum states differing vibronic side band behaviour is found.

We present tentative models, based on the influence of axial magnetic fields on the localization of the electronic wave function. The impact of spin/valley quantum numbers on the electron-vibron coupling is discussed.