You can not hear them, you can not see them - and yet they are fascinating. Nano researchers at the British universities of Lancaster and Oxford have, so to speak, built the smallest guitar in the world. In the journal "Nature Physics" the team around Edward Laird reports on the experiments, in which an extremely thin string is caused to vibrate by an electric current.
Researchers used a carbon nanotube that was attached to a metallic fixture at both ends. The tube was only three nanometers thick - or to remain the image of the guitar, as thin as a string that has been divided 100,000 times. The experimental setup was cooled extremely, to 0.02 degrees above the so-called absolute zero. It is 273.15 degrees Celsius or 0 Kelvin.
Micro guitar plays an A
The carbon nanotube was stored so that it could oscillate in the middle. In motion, it was brought by passing an electric current, in effect the team sent individual electrons through one after the other.
The individual electrons would have each set the nanotube in motion. If you set the parameters correctly, synchronize the movement, the string swing, the researchers report.
But what tone does the nano guitar play now? "The nanotube is significantly thinner than a guitar string, so it resonates at a much higher frequency in the ultrasonic range, so no one can hear it," says researcher Laird.
One can assign the frequency - it is at 231 megahertz, so at 231 million oscillations per second - but quite a sound. In the specific case, this is an "A", which is 21 octaves above a normal tuned instrument.
According to the researchers, the new technology could be used, among other things, in the further development of certain microscopes, so-called atomic force microscopes, or in measuring processes in so-called quantum liquids. These are liquids in which exotic quantum effects occur near absolute zero that can not be described with the laws of classical mechanics.