A special carbon molecule can act as multiple high-speed switches at the same time

 February 21, 2023

An international team of researchers, including those from the University of Tokyo's Institute for Solid State Physics, has demonstrated for the first time a switch analogous to a transistor made from a single molecule called fullerene.

The researchers were able to use fullerene to switch the path of an incoming electron in a predictable way by using a carefully tuned laser pulse. Depending on the laser pulses used, this switching process can be three to six orders of magnitude faster than switches in microchips. Fullerene switches in a network could produce a computer that is more powerful than electronic transistors, as well as unprecedented levels of resolution in microscopic imaging devices.

Physicists discovered that molecules emit electrons in the presence of electric fields and, later, in specific wavelengths of light more than 70 years ago. The electron emissions produced patterns that piqued people's interest but eluded explanation. This has changed as a result of a new theoretical analysis, the implications of which could lead not only to new high-tech applications but also improve our ability to scrutinise the physical world itself.

Hirofumi Yanagisawa and his colleagues theorised how the emission of electrons from excited molecules of fullerene should behave when exposed to specific types of laser light, and when tested, they discovered that their predictions were correct.

"We were able to control the way a molecule directs the path of an incoming electron using a very short pulse of red laser light," Yanagisawa explained. "Depending on the light pulse, the electron can either continue on its default path or be redirected in a predictable manner." So it's similar to train track switching points or electronic transistors, but much faster.

"We believe we can achieve a switching speed that is one million times faster than a conventional transistor." This could translate to real-world computing performance. However, if we can tune the laser to coax the fullerene molecule to switch in multiple directions at the same time, it could be like having multiple microscopic transistors in a single molecule. This could increase a system's complexity without increasing its physical size.

The underlying fullerene molecule is related to the perhaps slightly more well-known carbon nanotube, though instead of a tube, fullerene is a sphere of carbon atoms. When placed on a metal point—essentially the end of a pin—the fullerenes orient themselves in a certain way so they will direct electrons predictably. Fast laser pulses of femtoseconds, quadrillionths of a second, or even attoseconds, quintillionths of a second are focused on fullerene molecules to cause electron emission. This is the first time that laser light has been used to control electron emission from a molecule in this manner.

"This technique is similar to how a photoelectrochemical microscope generates images," Yanagisawa explained. "However, those can only achieve resolutions of about 10 nanometers, or ten billionths of a metre. Our fullerene switch improves on this, allowing for resolutions of around 300 picometers, or 300 trillionths of a metre.

In theory, because multiple ultrafast electron switches can be combined into a single molecule, a small network of fullerene switches could perform computational tasks much faster than conventional microchips. However, there are several obstacles to overcome, such as how to miniaturise the laser component, which is required to create this new type of integrated circuit. As a result, it may be many years before we see a smartphone powered by a fullerene switch.

By : PHYSOORG