MIT Researchers Uncover Unique Properties in Graphite through Innovative Nanoscale Microscopy Techniques
November 5, 2023 – MIT physicists have made a groundbreaking discovery in material physics by uncovering unique properties in graphite through innovative nanoscale microscopy techniques. The researchers, led by Assistant Professor Long Ju from the MIT Department of Physics, stacked five graphene layers in a precise order, creating what they call pentalayer rhombohedral stacked graphene. This material can exhibit insulating, magnetic, or topological characteristics, marking a significant advancement in the field.
Graphite, which is composed of graphene, has been the subject of intense research for the past two decades. However, it was only five years ago that researchers, including those at MIT, discovered that stacking individual sheets of graphene with slight twists can impart new properties to the material. This field, known as “twistronics,” has gained significant attention. However, the current work indicates that interesting properties can emerge without any twisting at all.
The key to this discovery was a novel microscope developed by Ju in 2021, known as Scattering-type Scanning Nearfield Optical Microscopy (s-SNOM). This microscope allowed the scientists to quickly and inexpensively identify and isolate the pentalayer rhombohedral stacked graphene, which is only a few billionths of a meter thick.
By attaching electrodes to a boron nitride sandwich, the researchers were able to tune the system with different voltages, leading to the emergence of three different phenomena depending on the number of electrons present. The material could be insulating, magnetic, or topological, which is a significant finding as topological materials allow for the unimpeded movement of electrons along the edges but not through the middle.
“Our work establishes rhombohedral stacked multilayer graphene as a highly tunable platform to study these new possibilities of strongly correlated and topological physics,” Ju explains.
In addition to its scientific implications, this discovery holds great potential for technological applications. The ability to tune graphite to exhibit these unique properties opens up new possibilities for electronic devices and quantum technologies.
The study, titled “Correlated insulators and Chern insulators in pentalayer rhombohedral-stacked graphene,” was published in the journal Nature Nanotechnology. The authors of the paper include Tonghang Han, Zhengguang Lu, Giovanni Scuri, Jiho Sung, Jue Wang, Tianyi Han, Kenji Watanabe, Takashi Taniguchi, Hongkun Park, and Long Ju.
This research was supported by various organizations, including 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.
With this groundbreaking discovery, the field of material physics takes a significant leap forward, paving the way for new advances in technology and our understanding of fundamental principles.