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MIT physicists flip pencil lead into “gold” » MIT Physics

MIT physicists flip pencil lead into “gold” » MIT Physics

2023-11-05 23:28:49

Isolate skinny flakes that may be tuned to exhibit three essential properties

MIT physicists have metaphorically turned graphite, or pencil lead, into gold by isolating 5 ultrathin flakes stacked in a selected order. The ensuing materials can then be tuned to exhibit three essential properties by no means earlier than seen in pure graphite.

“It’s type of like one-stop procuring,” says Long Ju, an assistant professor within the MIT Division of Physics and chief of the work, which is reported within the October 5 issue of Nature Nanotechnology. “Nature has loads of surprises. On this case, we by no means realized that every one of those attention-grabbing issues are embedded in graphite.”

Additional, he says, “It is rather uncommon materials to search out supplies that may host this many properties.”

Graphite consists of graphene, which is a single layer of carbon atoms organized in hexagons resembling a honeycomb construction. Graphene, in flip, has been the main target of intense analysis because it was first remoted about 20 years in the past. Then about 5 years in the past researchers together with a workforce at MIT found that stacking particular person sheets of graphene, and twisting them at a slight angle to one another, can impart new properties to the fabric, from superconductivity to magnetism. The sphere of “twistronics” was born.

 Within the present work, “we found attention-grabbing properties with no twisting in any respect,” says Ju, who can be affiliated with the Supplies Analysis Laboratory.

Professor Ju and colleagues
MIT Postdoctoral Affiliate Zhengguang Lu, Assistant Professor Lengthy Ju, and Graduate Pupil Tonghang Han within the lab. The three are authors, with seven others, of a paper in Nature Nanotechnology a couple of particular type of graphite (pencil lead).
Credit score: Ju Lab

 He and colleagues found that 5 layers of graphene organized in a sure order enable the electrons shifting round inside the fabric to speak with one another. That phenomenon, often called electron correlation, “is the magic that makes all of those new properties potential,” Ju says.

 Bulk graphite–and even single sheets of graphene–are good electrical conductors, however that’s it. The fabric Ju and colleagues remoted, which they name pentalayer rhombohedral stacked graphene, turns into way more than the sum of its elements.

Novel Microscope

Key to isolating the fabric was a novel microscope Ju constructed at MIT in 2021 that can rapidly and comparatively inexpensively decide quite a lot of essential traits of a fabric on the nanoscale. Pentalayer rhombohedral stacked graphene is just a few billionths of a meter thick.

Scientists together with Ju had been on the lookout for multilayer graphene that was stacked in a really exact order, often called rhombohedral stacking. Says Ju, “there are greater than 10 potential stacking orders whenever you go to 5 layers. Rhombohedral is only one of them.” The microscope Ju constructed, often called Scattering-type Scanning Nearfield Optical Microscopy, or s-SNOM, allowed the scientists to determine and isolate solely the pentalayers within the rhombohedral stacking order they had been thinking about.

Three In One

From there, the workforce connected electrodes to a tiny sandwich composed of boron nitride “bread” that protects the fragile “meat” of pentalayer rhombohedral stacked graphene. The electrodes allowed them to tune the system with totally different voltages, or quantities of electrical energy. The end result: they found the emergence of three totally different phenomena relying on the variety of electrons flooding the system.

“We discovered that the fabric may very well be insulating, magnetic, or topological,” Ju says. The latter is considerably associated to each conductors and insulators. Basically, Ju explains, a topological materials permits the unimpeded motion of electrons across the edges of a fabric, however not by the center. The electrons are touring in a single course alongside a “freeway” on the fringe of the fabric separated by a median that makes up the middle of the fabric. So the sting of a topological materials is an ideal conductor, whereas the middle is an insulator.

See Also

“Our work establishes rhombohedral stacked multilayer graphene as a extremely tunable platform to check these new potentialities of strongly correlated and topological physics,” Ju and his coauthors conclude in Nature Nanotechnology.

Along with Ju, authors of the paper are Tonghang Han and Zhengguang Lu. Han is a graduate pupil within the Division of Physics; Lu is a postdoctoral affiliate within the Supplies Analysis Laboratory. The 2 are co-first authors of the paper.

Different authors are Giovanni Scuri, Jiho Sung, Jue Wang and Hongkun Park of Harvard College; Kenji Watanabe and Takashi Taniguchi of the Nationwide Institute for Supplies Science in Japan, and Tianyi Han of MIT Physics.

This work was supported by a Sloan Fellowship; the U.S. Nationwide Science Basis; the U.S. Workplace of the Beneath Secretary of Protection for Analysis and Engineering; the Japan Society for the Promotion of Science KAKENHI;  the World Premier Worldwide Analysis Initiative of Japan; and the U.S. Air Pressure Workplace of Scientific Analysis.

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