Twistronics, a new field of quantum physics, involves stacking van der Waals materials to explore new quantum phenomena. Researchers at Purdue University have advanced this field by introducing quantum spin into twisted double bilayers of antiferromagnets, resulting in tunable Moiré magnetism. This breakthrough suggests new materials for spintronics and promises advances in memory and spin logic devices. Credit: SciTechDaily.com
Purdue quantum researchers have demonstrated tunable Moiré magnetism by twisting a double layer of antiferromagnet.
Twistronics is not a new dance move, exercise equipment, or new music fad. No, it’s much cooler than that. This is an exciting new development in quantum physics and materials science, in which van der Waals materials are layered on top of each other, like reams of paper that can be easily twisted and rotated while remaining flat. Scientists use these stacks to discover interesting quantum phenomena.
Adding the concept of quantum spin through twisted double bilayers of antiferromagnets allows for tunable Moiré magnetism. This suggests a new class of material platform for spintronics, the next step in twistonics. This new science could lead to promising memory and spin-logic devices and open entirely new avenues of spintronic applications in the world of physics.
![Combination of twistronics and spintronics](https://scitechdaily.com/images/Combining-Twistronics-With-Spintronics-777x682.jpg)
By twisting a van der Waals magnet, non-collinear magnetic states can be induced that can be electrically tuned to a large extent.Credit: Ryan Allen, Second Bay Studio
A team of quantum physics and materials researchers at Purdue University has introduced a twist that uses CrI to control the degrees of freedom of spin.3, using an interlayer antiferromagnetic coupling van der Waals (vdW) material as the medium. Their research, “Electrically tunable moiré magnetism in twisted double bilayers of chromium triiodide,” nature electronics.
“In this study, we fabricated twisted double bilayer CrI.3That is, a bilayer with a twist angle between the bilayers,” said Dr. Guanghui Cheng, co-lead author of the publication. “We report moiré magnetism with rich magnetic phases and significant tunability through electrical techniques.”
![Moiré superlattice structure of twisted double bilayer CrI3](https://scitechdaily.com/images/Moire-Superlattice-Structure-of-Twisted-Double-Bilayer-CrI3-777x463.png)
Moiré superlattice structure of twisted double layer (tDB) CrI3 and its magnetic behavior investigated by magneto-optic Kerr effect (MOKE). Section a above shows a schematic diagram of a moiré superlattice fabricated by interlayer torsion. Bottom panel: Non-collinear magnetic states can appear. Section b above shows that the MOKE results demonstrate the coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) order in the “moiré magnet” tDB CrI3 compared to the AFM order in the natural antiferromagnetic bilayer CrI3. is showing. Credits: Illustrations: Guanghui Cheng and Yong P. Chen
“We stacked the antiferromagnetic materials and twisted them, and now we have a ferromagnetic material,” Chen says. “This is also a striking example of the recently emerged ‘twisted’ or moiré magnetism in twisted he 2D materials, where the twist angle between two layers gives a powerful tuning knob, dramatically changing the material properties. Masu. ”
“To make twisted double bilayer CrI”3tear a piece of bilayer CrI.3We use what’s called a ‘tear and stack’ technique to rotate and stack onto other pieces,” Cheng explains. “Through magneto-optical Kerr effect (MOKE) measurement, a highly sensitive tool for investigating magnetic behavior down to several atomic layers, we observed the coexistence of ferromagnetic and antiferromagnetic order, which is a characteristic of Moiré magnetism, and further applied voltage. We have demonstrated -assisted magnetic switching. Such Moiré magnetism is a new form of magnetism characterized by spatially varying ferromagnetic and antiferromagnetic phases that periodically alternate according to a Moiré superlattice.”
To date, twistronics has primarily focused on tuning electronic properties such as twisted bilayers. graphene. The Purdue team wanted to introduce a twist to the spin degrees of freedom and chose to use CrI.3, interlayer antiferromagnetically coupled VdW material. The result that the stacked antiferromagnetic material twists on itself was made possible by fabricating samples with different twist angles. In other words, after fabrication, the twist angle of each device is fixed and MOKE measurements are performed.
Theoretical calculations for this experiment were performed by Upadhyaya and his team. This provided strong support for the observations made by Chen’s team.
“Our theoretical calculations reveal a rich phase diagram that includes noncollinear phases such as TA-1DW, TA-2DW, TS-2DW, and TS-4DW,” says Upadhyaya.
This study is part of ongoing research efforts by Cheng’s team. This research follows several related recent publications by the team on the new physics and properties of “2D magnets”.Emergence of field-tunable interfacial ferromagnetism in 2D antiferromagnetic heterostructures” was recently published. nature communications. This research avenue has exciting potential in the fields of twistonics and spintronics.
“The identified moiré magnets suggest a new class of materials platform for spintronics and magnetoelectronics,” says Chen. “The observed voltage-assisted magnetic switching and magnetoelectric effects may lead to promising memory and spin-logic devices. As a new degree of freedom, this twist can be applied to a wide range of homo/hetero double layers in vdW magnets and It opens up opportunities to pursue new physics and applications of spintronics.”
Reference: “Electrically tunable moiré magnetism in twisted double layers of chromium triiodide” Guanghui Cheng, Mohammad Mushfiqur Rahman, Andres Llacsahuanga Allcca, Avinash Rustagi, Xingtao Liu, Lina Liu, Lei Fu, Yanglin Zhu , Zhiqiang Mao, Kenji Watanabe, Takashi Taniguchi, Pramey Upadhyaya and Yong P. Chen, June 19, 2023, nature electronics.
DOI: 10.1038/s41928-023-00978-0
The team is primarily from Purdue, with two lead authors contributing equally: Dr. Guanghui Cheng and Mohammad Mushfiqur Rahman. Cheng was a postdoctoral fellow in Dr. Yong P. Chen’s group at Purdue University and is currently an assistant professor at Tohoku University’s Advanced Institute for Materials Research (AIMR, where Cheng is also a principal investigator). Mohammad Mushfiqur Rahman is a PhD student in Dr. Pramey Upadhyaya’s group. Chen and Upadhyaya are both corresponding authors of this publication and professors at Purdue University. Chen is the Karl Lach Horowitz Professor of Physics and Astronomy, professor of electrical and computer engineering, and director of the Purdue Institute for Quantum Science and Engineering. Upadhyaya is an assistant professor of electrical and computer engineering. Other Purdue-affiliated team members include Andres Llacsahuanga Allcca (doctoral student), Dr. Lina Liu (postdoc), and Dr. Lei Fu (postdoc) in Chen’s group; Dr. Avinash Rustagi (postdoc) in Upadhyaya’s group; and Dr. Xingtao Liu. (Former research assistant at Burke Nanotechnology Center).
This research was supported in part by the U.S. Department of Energy (DOE) Office of Science through the Quantum Science Center (QSC, National Quantum Information Science Research Center) and the Department of Defense (DOD) Multidisciplinary University Research Initiative (MURI) program (FA9550-). Supported. 20-1-0322). Cheng and Chen also received partial support from WPI-AIMR, JSPS KAKENHI Fundamental Science A (18H03858), New Science (18H04473 and 20H04623), and the Tohoku University FRiD program during the early stages of their research.
Upadhyaya also acknowledges support from the National Science Foundation (NSF) (ECCS-1810494). Bulk CrI3 The crystals are provided by Zhiqiang Mao’s group at Pennsylvania State University with support from the U.S. Department of Energy (DE-SC0019068). hBN bulk crystals were produced with Kenji Watanabe of the National Institute for Materials Science, Japan, with support from the JSPS KAKENHI (grant numbers 20H00354, 21H05233, and 23H02052) and the Ministry of Education, Culture, Sports, Science and Technology’s World Premier International Research Center Initiative (WPI). Provided by Takashi Taniguchi.