MIT physicists and colleagues have metaphorically turned graphite, or pencil lead, into gold by isolating five ultrathin flakes stacked in a specific order. The resulting material can then be tuned to exhibit three important properties never before seen in natural graphite.
"It is kind of like one-stop shopping," says Long Ju, an assistant professor in the MIT Department of Physics and leader of the work, which is reported in the Nature Nanotechnology. "In this case, we never realized that all of these interesting things are embedded in graphite."
Further, he says, "It is very rare to find materials that can host this many properties."
Graphite is composed of graphene, which is a single layer of carbon atoms arranged in hexagons resembling a honeycomb structure. Graphene, in turn, has been the focus of intense research since it was first isolated about 20 years ago. Then about five years ago researchers including a team at MIT discovered that stacking individual sheets of graphene, and twisting them at a slight angle to each other, can impart new properties to the material, from superconductivity to magnetism. The field of "twistronics" was born.
In the current work, "we discovered interesting properties with no twisting at all," says Ju, who is also affiliated with the Materials Research Laboratory.
He and colleagues discovered that five layers of graphene arranged in a certain order allow the electrons moving around inside the material to talk with each other. That phenomenon, known as electron correlation, "is the magic that makes all of these new properties possible," Ju says.
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