Liquid-induced damping of mechanical feedback effects in single electron tunneling through a suspended carbon nanotube

Significance Statement

Suspended single wall carbon nanotubes can act as nearly dissipation-free nano-electromechanical beam resonators at cryogenic temperatures, with typical resonance frequencies on the order of 100MHz. While this leads to a rich spectrum of fascinating physical phenomena, it can also make measurements of the electronic nanotube properties more difficult. In transport spectroscopy measurements of carbon nanotube-based quantum dots, even without application of a rf driving signal, strong feedback between single electron tunneling and vibrational motion induces switching phenomena and strong distortions of the distinct “Coulomb diamond” spectroscopic patterns.

We demonstrate that the inert but viscous 3He/4He liquid present in the mixing chamber of a dilution refrigerator (diluted phase) can be used to dampen vibrational motion and restore regular transport spectroscopy behaviour. This beautifully confirms the mechanical origin of the observed switching phenomena. Additionally, as a consequence, measurements in 3He/4He liquid also provide a way to perform transport spectroscopy over much wider parameter ranges compared to a vacuum environment – in particular, at high bias voltages and at high transparency of the quantum dot – lead barriers.

Journal Reference

Appl. Phys. Lett. 107, 123110 (2015)

R. Schmid, P. L. Stiller, Ch. Strunk, A. K. Hüttel

Institute for Experimental and Applied Physics, University of Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany

 

Abstract

In single electron tunneling through clean, suspended carbon nanotube devices at low temperature, distinct switching phenomena have regularly been observed. These can be explained via strong interaction of single electron tunneling and vibrational motion of the nanotube. We present measurements on a highly stable nanotube device, subsequently recorded in the vacuum chamber of a dilution refrigerator and immersed in the 3He/ 4He mixture of a second dilution refrigerator. The switching phenomena are absent when the sample is kept in the viscous liquid, additionally supporting the interpretation of dc-driven vibration. Transport measurements in liquid helium can thus be used for finite bias spectroscopy where otherwise the mechanical effects would dominate the current.

© 2015 AIP Publishing LLC

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