Gary Steele's TU-Delft Website

About me

I am currently a post-doctoral researcher in the Quantum Transport Group at the Delft University of Technology. My reserach is focussed on fabricating double quantum dots in carbon nanotubes with on-chip charge detectors with single-electron sensistivity. Our ultimate goal is to measure the relaxation and coherence times of single electron spins in carbon nanotube quantum dots.

On the road to this goal, I have developed a new type of clean nanotube device. In addition to pursuing spin qubit devices with these nanotubes, I am also exploring their remarkable electrical, mechanical and optical properties.

Ultra-clean carbon nantotubes

In order to achieve the control over single electron confinement needed for the spin qubit experiments, I recently developed a new method of making "ultra-clean" carbon nanotube devices that include multiple gates. Here, we perform all fabrication before growing the nanotube, and then grow the nanotube across the predefined structure in the last step. After fabrication, the device looks something like this:

In this image, you see a carbon nanotube hanging across between two metal electrodes (electrodes are shown in light blue). Underneath the bottom of the trench is a silicon backgate, and underneath each metal electrodes is an additional silicon gate. This devices gives us three gates we can use to tune the confinement of single electrons in the nanotube. To learn more about how we make these devices and use them to control single electrons, see my Nature Nanotechnology paper below.

The suspended nanotubes in these devices also have remarkable mechanical properties: in particular, because the nanotube is freely hanging, it can vibrate, like a nanometer-sized guitar string. Remarkably, the mechanical vibration of this nano-guitar string has an incredibly high quality factor of more than 150 000! This means that if we "pluck" the nanotube guitar string, it will vibrate back and forth 150 000 times before the motion is damped. For more information on nanotubes as high-Q resonators, see our 2009 paper in Nano Letters below.

Publicity

A new paper of mine "Strong Coupling Between Single Electron Tunneling and Nanomechanical Motion" appeared online on Science Express. The press office at TU-Delft wrote this nice press release: 'Nano violin string' by Delft researchers in Science

In these experiments, we are able to both "tune" and "pluck" a nanotube violin string using single electrons. As a fun demonstration, you can "hear" what our data sounds like in this video:

News & Perspectives

Nanoelectromechanical systems: Show of strength Marc Bockrath, News & Views, Nature Nanotechnology 4, 619 (October 2009)

Coupling Strongly, Discretely James Hone and Vikram V. Deshpande, Perspectives, Science 325, 1084 (28 August 2009)

Nanotubes keep rolling on Editorial, Nature Nanotechnology, 4 465 (August 2009)

Quantum dots: When a barrier is not an obstacle Mahn-Soo Choi, News & Views, Nature Nanotechnology, 4, 347 (June 2009)

Publications

G. A. Steele, A. K. Hüttel, B. Witkamp, M. Poot, H. B. Meerwaldt, L. P. Kouwenhoven, H. S. J. van der Zant, Strong Coupling Between Single-Electron Tunneling and Nanomechanical Motion Science 325, 1103 (2009)

F. A. Zwanenburg, A. A. van Loon, G. A. Steele, C. E. W. M. van Rijmenam, T. Balder, Y. Fang, C. M. Lieber, and L. P. Kouwenhoven, Ultrasmall silicon quantum dots J. Appl. Phys. 105, 124314 (2009)

A. K. Huettel, G. A. Steele, B. Witkamp, M. Poot, L. P. Kouwenhoven, H. S. J. van der Zant, Carbon nanotubes as ultra-high quality factor mechanical resonators Nano Lett, 2009, 9 (7), pp 2547 cond-mat

G. A. Steele, G. Gotz, L. P. Kouwenhoven, Tunable few-electron double quantum dots and Klein tunnelling in ultra-clean carbon nanotubes Nature Nanotechnology 4, 363 - 367 (2009) cond-mat

G. Gotz, G.A. Steele, W. Vos, L.P. Kouwenhoven, Real Time Electron Tunneling and Pulse Spectroscopy in Carbon Nanotube Quantum Dots Nano Lett., 2008, 8 (11), p 4039 cond-mat

G. A. Steele, R. C. Ashoori, L. N. Pfeiffer, K. W. West Imaging Transport Resonances in the Quantum Hall Effect Phys. Rev. Lett. 95, 136804 (2005) cond-mat