By Elizabeth A. Thomson, MIT Products Lab
November 5, 2023
Even more, he states, “It is very unusual product to find materials that can host this lots of residential or commercial properties.”
The Rise of “Twistronics”.
Graphene, in turn, has actually been the focus of extreme research study considering that it was initially separated about 20 years ago. About 5 years ago researchers consisting of a group at MIT found that stacking private sheets of graphene, and twisting them at a minor angle to each other, can impart new properties to the material, from superconductivity to magnetism.
In the current work, “we found intriguing residential or commercial properties without any twisting at all,” says Ju, who is also connected with the Materials Research Laboratory.
Artists rendition of the electron connection, or ability of electrons to talk with each other, that can happen in an unique kind of graphite (pencil lead). Credit: Sampson Wilcox, MIT Research Laboratory of Electronics.
He and colleagues discovered that five layers of graphene set up in a particular order allow the electrons moving inside the material to talk with each other. That phenomenon, referred to as electron connection, “is the magic that makes all of these brand-new homes possible,” Ju says.
Bulk graphite– and even single sheets of graphene– are excellent electrical conductors, but thats it. The material Ju and colleagues separated, which they call pentalayer rhombohedral stacked graphene, becomes much more than the sum of its parts.
A Novel Microscope and Its Discoveries.
Key to separating the product was a novel microscope Ju developed at MIT in 2021 that can quickly and fairly inexpensively determine a variety of essential characteristics of a material at the nanoscale. Pentalayer rhombohedral stacked graphene is just a couple of billionths of a meter thick.
Scientists including Ju were looking for multilayer graphene that was stacked in a very exact order, known as rhombohedral stacking. The microscope Ju developed, known as Scattering-type Scanning Nearfield Optical Microscopy, or s-SNOM, permitted the researchers to recognize and isolate only the pentalayers in the rhombohedral stacking order they were interested in.
Multifaceted Material Phenomena.
From there, the group attached electrodes to a tiny sandwich made up of boron nitride “bread” that safeguards the fragile “meat” of pentalayer rhombohedral stacked graphene. The electrodes enabled them to tune the system with various voltages, or quantities of electrical energy. The outcome: they found the development of three different phenomena depending upon the number of electrons flooding the system.
MIT Postdoctoral Associate Zhengguang Lu, Assistant Professor Long Ju, and Graduate Student Tonghang Han in the laboratory. The 3 are authors, with seven others, of a paper in Nature Nanotechnology about a special kind of graphite (pencil lead). Credit: Ju Lab.
” We discovered that the material might be insulating, magnetic, or topological,” Ju states. The latter is rather associated to both insulators and conductors. Basically, Ju describes, a topological product permits the unobstructed motion of electrons around the edges of a product, but not through the middle. The electrons are taking a trip in one direction along a “highway” at the edge of the material separated by a mean that comprises the center of the product. The edge of a topological material is an ideal conductor, while the center is an insulator.
” Our work develops rhombohedral stacked multilayer graphene as a highly tunable platform to study these brand-new possibilities of highly associated and topological physics,” Ju and his coauthors conclude in Nature Nanotechnology.
Reference: “Correlated insulator and Chern insulators in pentalayer rhombohedral-stacked graphene” by Tonghang Han, Zhengguang Lu, Giovanni Scuri, Jiho Sung, Jue Wang, Tianyi Han, Kenji Watanabe, Takashi Taniguchi, Hongkun Park and Long Ju, 5 October 2023, Nature Nanotechnology.DOI: 10.1038/ s41565-023-01520-1.
In addition to Ju, authors of the paper are Tonghang Han and Zhengguang Lu. Han is a graduate trainee in the Department of Physics; Lu is a postdoctoral associate in the Materials Research Laboratory. The 2 are co-first authors of the paper.
Other authors are Giovanni Scuri, Jiho Sung, Jue Wang and Hongkun Park of Harvard University; Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan, and Tianyi Han of MIT Physics.
This work was supported by a Sloan Fellowship; the U.S. National Science Foundation; the U.S. Office of the Under Secretary of Defense for Research and Engineering; the Japan Society for the Promotion of Science KAKENHI; the World Premier International Research Initiative of Japan; and the U.S. Air Force Office of Scientific Research.
About 5 years ago researchers consisting of a group at MIT discovered that stacking specific sheets of graphene, and twisting them at a slight angle to each other, can impart new residential or commercial properties to the product, from superconductivity to magnetism.” We found that the product might be insulating, magnetic, or topological,” Ju says. Essentially, Ju discusses, a topological material allows the unobstructed movement of electrons around the edges of a product, but not through the middle. The electrons are taking a trip in one instructions along a “highway” at the edge of the product separated by a typical that makes up the center of the product. The edge of a topological material is a perfect conductor, while the center is an insulator.
MIT scientists have uncovered special homes in graphite by stacking five graphene layers in a precise order. This pentalayer rhombohedral stacked graphene can manifest insulating, magnetic, or topological attributes, marking a substantial discovery in product physics utilizing ingenious nanoscale microscopy strategies.
Separate thin flakes that can be tuned to show three essential homes.
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 3 crucial properties never ever before seen in natural graphite.
” It is type 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 problem of Nature Nanotechnology. “Nature has a lot of surprises. In this case, we never ever realized that all of these interesting things are embedded in graphite.”
