For decades, scientists have explored the potential of two-dimensional matter to change our world. A 2D object is just a single layer of atoms. In them, subatomic particles such as electrons can move in two directions. This simple resistance can trigger special electronic behavior, giving “weird” properties such as strange magnetism, extreme behavior and other collective behavior between electrons (A new twist on graphite) – all of which can be useful in computers, communications, energy and other fields.
But researchers often think that these amazing 2D properties are only available in single sheets or small packages. The so-called “larger” forms of these elements – and their complex 3D atomic structure – should behave differently. Or so they thought.
In a paper published on July 19 in Nature, a group of researchers led by the University of Washington reports that it is possible to imbue graphite – a large 3D substance found in the number 2 pencil – in a physical object similar to of graphite’s 2D counterpart, graphene.
Not only is this progress (A new twist on graphite) unexpected, but the team also believes that their method will be used to test whether similar large objects can also take on 2D objects. If so, 2D paper will not be the only place where scientists make technological changes. In large, 3D objects can be useful.
“Stacking one layer on one layer – or two layers on top of two layers – has been the focus of unlocking new physics in 2D materials for many years now. In these experimental ways, that’s where a lot of interesting things come out,” said author Matthew Yankowitz, assistant professor of physics and materials science and engineering at the UW.
“But what if you adding layers? Eventually, it has to stop, doesn’t it? This is what the theory suggests. But in this case, the idea is not good. It is possible to mix 2D objects into 3D objects.
The team, which also includes researchers from Osaka University and the National Institute of Materials Science in Japan, recreated a method that is often used to analyze and manipulate the properties of 2D objects: using small parts to turn 2D sheets of paper.
Yankowitz and his colleagues placed a single layer of graphene on a thin crystal of large graphite, and introduced a transition angle of about 1 degree between the graphite and graphene. They discovered unexpected new electrical properties not only in the curved interface, but also in the bulk graphite.
Transients are key to creating these devices, said Yankowitz, who is also a faculty member at the UW Clean Energy Institute and the UW Institute for Nano-Engineered Systems.
The rotational motion between 2D sheets, such as two sheets of graphene, creates a so-called moire pattern, which changes the flow of charged particles such as electrons and causes strange phenomena in the to do that.
In experiments conducted by the UW with graphite and graphene, the reverse angle also produced moiré patterns, with surprising results.
Although a single sheet of graphene on the surface of a large curved crystal, the researchers found that the electrical properties of the whole material were different from that of graphite.
But when they were exposed to a magnetic field, the electrons inside the graphite crystals took on unusual properties similar to those of the electrons at the curved interface. Basically, the graphene-graphite interface is uniquely curved and mixed with other graphite.
“Although we only created the moiré pattern on the surface of the graphite, the results show up throughout the crystal,” said lead author Dacen Waters, a postdoctoral researcher in physics at the UW.
For 2D sheets, the moiré pattern generated can be useful for quantum computing and other applications. The production of analogs and 3D objects opens up new ways to study unusual and exotic situations and how they can be presented in the laboratory and in our everyday life.
“The whole crystal takes this 2D shape,” said lead author Ellis Thompson, a UW physics PhD student. “This is a new method that affects the behavior of electrons in large objects.”
Yankowitz and his team believe that their method of creating transitions between graphene and graphite crystals can be used to create 2D-3D hybrids of its sister materials, including tungsten ditelluride and zirconium pent telluride.
This can open up new ways to manipulate the properties of large scale objects using a single 2D interface. “This system can become a very rich playground for studying new and exciting physical objects with mixed 2D and 3D properties,” said Yankowitz.
Source: University of Washington
