Researchers from the City University of Hong Kong (CityUHK) and local collaborators have made a groundbreaking discovery of a new vortex electric field, poised to revolutionize future electronic, magnetic, and optical devices.
This research holds immense promise for significantly enhancing the performance of various devices, particularly by improving memory stability and accelerating computing speeds. As further studies unfold, the implications of this vortex electric field could soon extend into fields such as quantum computing, spintronics, and nanotechnology.
“Previously, generating a vortex electric field required expensive thin film deposition techniques and complex procedures. However, our research has demonstrated that a simple twist in bilayer 2D materials can easily induce this vortex electric field,” said Professor Ly Thuc Hue of the Department of Chemistry and a core member of the Centre of Super-Diamond and Advanced Films at CityUHK.
To create a truly clean interface, researchers have traditionally synthesized bilayers directly, but this often limits the flexibility in twisting angles, particularly for low-angle twists. Professor Ly and her team have revolutionized this process with their groundbreaking ice-assisted transfer technique. This innovative method has been pivotal in achieving pristine interfaces between bilayers, allowing for unprecedented manipulation and creation of twisted bilayers.
While earlier studies were restricted to twist angles of less than 3 degrees, this new technique empowers the team to explore a vast array of twist angles from 0 to 60 degrees through a combination of synthesis and artificial stacking using ice-assisted transfer.
The novel discovery of a new vortex electric field in the twisted bilayer has also led to the formation of a 2D quasicrystal, which could improve future electronic, magnetic, and optical devices.
Quasicrystals are sought-after irregularly ordered structures because of their low thermal and electrical conductivity, making them suitable for high-strength surface coatings like those used in frying pans.
As stated by Professor Ly, these structures offer a diverse array of applications since the generated vortex electric field varies according to the twist angle. The quasicrystals can lead to a more durable memory effect for electronic devices, rapid mobility and processing speeds for computing, lossless polarization switching, new optical effects with polarization, and progress in spintronics.
The team faced numerous challenges in their journey to achieve the new observation. Initially, they needed to establish a clean interface between bilayers, which led them to invent a novel technique that utilizes ice as a transfer medium, a first for this domain.
By synthesizing and transferring 2D materials with a thin layer of ice, the team was able to create clean interfaces that were easy to handle. In comparison to other methods, this ice-assisted transfer approach is more efficient, quicker, and more economical.
Next, they had to tackle the difficulty of analyzing the material. Their breakthrough came with the application of four-dimensional transmission electron microscopy (4D-TEM) in collaboration with other researchers. During the testing phases, they successfully created a twisted bilayer 2D structure and observed a new vortex electric field.
The research team is excited to build on their recent findings regarding twist angles, as they see a vast array of applications emerging from their work. They plan to focus on the next phases of their study, which will include experimenting with additional material manipulations—such as testing the feasibility of stacking more layers—and investigating if similar phenomena can be achieved with different materials.
Having secured a patent for their ice-assisted transfer method, the team is excited to see if their technique can facilitate additional global discoveries now that clean bilayer interfaces can be achieved without costly and complex procedures.
“This study had the potential to ignite a new field focused on twisting vortex fields in nanotechnology and quantum technology,” Professor Ly concluded, emphasizing that the discovery, though still in the early stages in terms of application, could be a major game-changer in device applications such as memory, quantum computing, spintronics, and sensing devices.
Journal reference:
- Chi Shing Tsang, Xiaodong Zheng, Tong Yang, Zhangyuan Yan, Wei Han, Lok Wing Wong, Haijun Liu, Shan Gao, Ka Ho Leung, Chun-Sing Lee, Shu Ping Lau, Ming Yang, Jiong Zhao, Thuc Hue Ly. Polar and quasicrystal vortex observed in twisted-bilayer molybdenum disulfide. Science, 2024; DOI: 10.1126/science.adp7099