Scientists at the University of Bath have taken an important step in understanding the interactions between layers of atomic thin materials arranged in layers. They hope their research will accelerate the discovery of new artificial materials, resulting in the design of electronic components much smaller and more efficient than anything known today.
Smaller is always better in the world of microchips, but there̵7;s a limit to how much you can shrink a silicon component without overheating and breaking, and we’re almost there. Researchers are working on a group of atom-thin materials that can be assembled into stacks. The properties of any final material depend both on the choice of raw materials and the angle at which one layer is arranged on top of another.
Dr. Marcin Mucha-Kruczynski, head of research from the Department of Physics, said: “We have found a way to determine how strong atoms are in different layers of a stack are linked together and We demonstrated the application of our idea of a structure made of layers of graphene. “
The study of Bath, published in Nature Communications, is based on previous research into graphene – a crystal characterized by thin sheets of carbon atoms arranged in a honeycomb design. In 2018, scientists at Massachusetts Institute of Technology (MIT) discovered that when two layers of graphene were stacked and then twisted together at a ‘magic’ angle of 1.1 °, they produced a material with superconducting properties. This is the first time that scientists have created a superconducting material made entirely of carbon. However, these properties disappeared with the smallest angle change between the two graphene layers.
Since the discovery of MIT, scientists around the world have been trying to apply this ‘stacking and twisting’ phenomenon to other ultrathin materials, placing two or more different structures atoms. together in the hope of forming completely new materials with special qualities.
“In nature, you cannot find materials where each atomic layer is different,” said Dr. Mucha-Kruczynski. “Furthermore, two conventional materials can only be put together in a particular way because chemical bonds need to form between layers. But for materials like graphene, there are only bonds.” the chemistry between atoms on the same plane is strong. The force between planes – known because of the van der Waals interaction – is very weak and this allows the material layers to be twisted together. “
The challenge for scientists today is to make the process of discovering new, multi-layered materials as efficient as possible. By finding a formula that allows them to predict the outcome when two or more materials are stacked, they’ll be able to streamline a lot of their research.
In this area, Dr. Mucha-Kruczynski and his colleagues at Oxford University, Peking University and the ELETTRA Synchrotron in Italy are expected to make a difference.
Dr Mucha-Kruczynski said: “The number of combinations of materials and the number of angles in which they can be twisted is too great to try in the lab, so what we can predict is very important important ”.
Researchers have shown that the interaction between two layers can be determined by studying the three-layer structure, where the two layers are assembled as you can see in nature, while the third layer is twisted. again. They used angular resolution spectroscopy – a process in which strong light pushes electrons out of the sample to be able to measure the energy and momentum from the electrons, thus providing insight. material properties – to determine the strength of two carbon atoms at a given distance from each other. They also demonstrated that their results can be used to predict the properties of other stacks made of the same layers, even when the torsion between layers is different.
The list of atomically thin materials like graphene is growing continuously. It has included dozens of entries showing a wide range of properties, from insulation to superconductivity, transparency to optical action, brittleness to versatility. The latest discovery provides a method for experimentally determining the interactions between layers of any of these materials. This is necessary to predict the properties of the more complex stacks and to efficiently design new devices.
Dr. Mucha-Kruczynski believes it may take 10 years before stacking and twisted materials find practical everyday application. “It took a decade for graphene to move from the lab to something useful, so with a bit of optimism I’m looking forward to a similar timeline for applying to new materials,” he said.
Based on the results of their latest research, Dr. Mucha-Kruczynski and his team are now focusing on twisted stacks made from layers of transition metal dichalcogenide (a large group of materials with two types of raw materials). very different particles – a metal and a chalcogen, such as sulfur). Some of these stacks have shown fascinating electronic behavior that scientists have yet to explain.
Dr Mucha-Kruczynski explains: “Because we are dealing with two completely different materials, studying these stacks is very complicated. “However, we hope that from time to time we will be able to predict the properties of different stacks and design new multifunctional materials.”
Take the guesswork out of the twistronics
JJP Thompson et al, Determination of the interatomic coupling between two-dimensional crystals by angular resolution spectroscopy, Nature Communications (Year 2020). DOI: 10.1038 / s41467-020-17412-0
Provided by University of Bath
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