Ever since graphene hit the science scene in 2003, the two-dimensional carbon material has been proving the power of flatness — with applications ranging from creating ultrasonic microphones to improving heat regulation in smartphones. Now, scientists are claiming that 3D forms of graphene could open up even more opportunities.
The simplest example of the 3D graphene-like structures, described by University of Oklahoma scientists in a paper published in the journal Physical Review Letters, is known as a hyper-honeycomb. The researchers are still working to create these theoretically possible structures in reality — and they expect that a hyper-honeycomb would be even more stable than the poster child for permanence: the diamond.
Like diamonds, graphene is made of only carbon atoms (though natural diamonds are imperfect and may contain trace amounts of other atoms). But unlike those in diamonds, the carbon atoms in true graphene are arranged so that they form a completely two-dimensional material. The arrangement of carbon atoms that makes this unusual, 2D material possible happens to look just like a classic honeycomb pattern — with each carbon atom connected to three other carbon atoms, as shown in the image below.
The fact that graphene is a 2D material is neat, but what really has the scientific community so excited about graphene are its remarkable properties. One example is that the honeycomb-esque configuration of the carbon atoms in graphene causes electrons – the particles that carry electrical currents – to behave in a bizarre way. When electrons move through graphene, they act much like they do when moving close to the speed of light.
The conditions under which this strange behavior occurs are known as Dirac points — and they simply don't exist in most materials. But they are still not as rare as Dirac loops – the 3D version of Dirac points – which have never been observed. In this recent paper, scientists suggest that hyper-honeycombs are where scientists might at last behold Dirac loops.
"This is the first simple system to display Dirac loops," lead study author Kieran Mullen told Phys.org. "Dirac loops are a behavior not yet seen in electronic systems. The existence of such a loop would have strong effects on how electrons flow through the system and on how they behave in the presence of a magnetic field."
Creating hyper-honeycombs and related 3D structures will be challenging, but Mullen and his colleagues propose that it is possible with current technology.
Photo: Brian Jeffery Beggerly | Flickr