Physicists have developed a technique to precisely align supermoire lattices, revolutionizing the possibilities of next-generation moire quantum materials.
Physicists at the National University of Singapore (NUS) have developed a technique to precisely control the alignment of supermoire lattices using a set of golden rules, paving the way for advances in next-generation moire quantum materials.
super moire lattice
Moiré patterns are formed when two identical periodic structures are superimposed with a relative twist angle, or when two different periodic structures are superimposed with or without a twist angle. The twist angle is the angle between the crystal orientations of two structures.For example, when graphene When the layered materials hexagonal boron nitride (hBN) and hexagonal boron nitride (hBN) are stacked on top of each other, the atoms in the two structures do not align perfectly, resulting in a pattern of interference fringes called a moiré pattern. This will result in an electronic reconfiguration.
Moiré patterns in graphene and hBN have been used to create new structures with exotic properties such as topological currents and Hofstadter butterfly states. When two moiré patterns are stacked on top of each other, a new structure called a supermoiré lattice is created. Compared to traditional single moire materials, this supermoire lattice expands the range of tunable material properties, enabling the possibility of use in a wider range of applications.
Achievements of NUS Physics Department
A research team led by Professor Ariand of the NUS Department of Physics has developed a technology and successfully realized a controlled arrangement of hBN/graphene/hBN supermoiré lattices. This technique allows two moiré patterns to be precisely placed on top of each other. Meanwhile, the researchers also developed “three golden rules” to guide the use of the technique to create supermoire lattices.
The results of this study were recently published in the journal nature communications.
Challenges and solutions
There are three main challenges to creating graphene supermoiré lattices. First, traditional optical alignment relies heavily on straight edges of graphene, but finding suitable graphene flakes is time-consuming and labor-intensive. Second, even if we use a straight-edge graphene sample, the probability of obtaining a doubly aligned supermoire lattice is as low as 1/8 due to uncertainties in its edge chirality and lattice symmetry. . Third, although edge chirality and lattice symmetry can be determined, alignment errors are often large (greater than 0.5 degrees) because it is physically difficult to align two different lattice materials.
Dr. Junxiong Hu, lead author of the research paper, said: “Our technology can help solve real-world problems. Many researchers have told us that it typically takes them nearly a week to create a sample. Our technology can significantly reduce manufacturing time. quality can be significantly improved. Accuracy sample. ”
technical insight
The scientists first use a “30° rotation technique” to control the alignment of the top hBN and graphene layers. We then use the “flip-over technique” to control the placement of the top His hBN layer and the bottom His hBN layer. Based on these two methods, the symmetry of the lattice can be controlled and the band structure of the graphene supermoire lattice can be tuned. They also showed that adjacent graphite edges can act as guides for stacking alignment. In this study, he created 20 moiré samples with an accuracy of better than 0.2 degrees.
Professor Ariand said: “We have established three golden rules for the technique that will serve many researchers in the two-dimensional materials community. Many working on other strongly correlated systems, such as magic-angle twisted bilayer graphene and ABC stacking multilayer graphene, “Scientists across the world are also expected to benefit from our research. We hope that this technological improvement will accelerate the development of next-generation moiré quantum materials.”
How it will be done in the future
The research team is currently leveraging this technique to create single-layer graphene supermoire lattices and investigate the unique properties of this material system. Additionally, they are extending their current techniques to other material systems and discovering other new quantum phenomena.
Reference: “Orientation control of supermoire lattices in doubly oriented graphene heterostructures” Junxiong Hu, Junyou Tan, Mohammed M. Al Ezzi, Udvas Chattopadhyay, Jian Gou, Yuntian Zheng, Zihao Wang, Jiayu Chen, Reshmi Thottathil, Jiangbo Luo , by Kenji Watanabe, Takashi Taniguchi, Andrew Tai Sheng Wee, Shafik Adam, A. Ariand, July 12, 2023, nature communications.
DOI: 10.1038/s41467-023-39893-5