Graphite to Gold...



Artist’s rendition of the electron correlation, or the ability of electrons to talk with each other, can occur in a special kind of graphite (pencil lead). @ Sampson Wilcox, MIT Research Laboratory of Electronics


Topics: Entanglement, Graphene, Materials Science, Nanomaterials, Nanotechnology

 MIT physicists 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 October 5 issue of Nature Nanotechnology. “Nature has plenty of surprises. 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.

 Bulk graphite--and even single sheets of graphene--are good electrical conductors, but that’s it. The material Ju and colleagues isolated, which they call pentalayer rhombohedral stacked graphene, becomes much more than the sum of its parts.

 Correlated insulator and Chern insulators in pentalayer rhombohedral-stacked graphene

 Tonghang Han, Zhengguang Lu, Giovanni Scuri, Jiho Sung, Jue Wang, Tianyi Han, Kenji Watanabe, Takashi Taniguchi, Hongkun Park & Long Ju


Massachusetts Institute of Technology


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