3D rendering of graphene molecular structure hexagonal geometric form.Credit: Roman Milert / Alamy Stock Photo
Physicists have discovered a way to store and process data in graphene that goes beyond the simple manipulation of flow and charge of electrons. In simulation studies, they have shown that a specific type of laser light could tune the properties of electrons in graphene, unlocking its potential for information processing1.
Atom-thick graphene has no band gap — the energy difference between valence bands and conduction bands of electrons. When researchers exposed graphene to the laser light, it created a band gap, which unmasked a 'valley state' in two-dimensional graphene, allowing electrons to occupy the valley between valence and conduction bands. Electrons are known to jump from valence bands to conduction bands. This jump dictates the optical, electrical and magnetic properties of any solid crystals.
“In graphene, electrons can be selectively transferred from valence to conduction bands at a selected valley, whereas the electrons at other valleys are unaffected,” says lead researcher, Gopal Dixit, from the Indian Institute of Technology in Mumbai. "We can then see it as 1 for the first valley and 0 for the other valley."
These valleys in graphene may be used to encode, process and store quantum information at room temperature, Dixit adds. Such a development, he says, could open doors to miniature, general-purpose quantum computers that could be used by non-scientists, much like laptops are.
Since graphene is a material with zero band gaps, light cannot selectively excite its electrons. To overcome this obstacle, the researchers used ultrashort pulses of laser that fit with the structure of one valley and not the other. “We can tune this form so that it can fit to the other valley and not to the previous one,” Dixit explains.
This enables the use of graphene's valleys to effectively ‘write’ information. Flashes of light can cause electrons in graphene to wiggle several hundred trillion times a second. In theory, this could give rise to high-speed information processing, exceeding modern computational speeds by a million times.
“This research identifies a simple light-assisted protocol for achieving control of the valley population of graphene electrons,” says Krishnendu Sengupta, a physicist from the Kolkata-based Indian Association for the Cultivation of Science, who was not involved.
“However, the importance of electron-electron interaction and the role of disorder, which is always present in realistic materials, need to be addressed before the findings could be used in technology,” Sengupta notes.
But Dixit says that graphene-based quantum computers will offer a faster way to perform molecular simulations, big data analysis, deep learning and other computationally intensive tasks.
