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Physicists are accelerating the search for revolutionary artificial atomic materials


This visualization shows graphene layers that are used for membranes. Photo credit: University of Manchester

Scientists at the University of Bath have taken an important step towards understanding the interaction between layers of atomically thin materials arranged in stacks. They hope their research will accelerate the discovery of new man-made materials, which will lead to the development of electronic components that are far smaller and more efficient than anything known today.

Smaller is always better in the electronic circuit world, but there is a limit to how far you can shrink a silicon component without it overheating and falling apart, and we are close to reaching it. The researchers are investigating a group of atomically thin materials that can be put together in stacks. The properties of an end material depend both on the choice of raw materials and on the angle at which a layer is placed on top of one another.

Dr. Marcin Mucha-Kruczynski, who led research in the physics department, said: “We have found a way to determine how strongly atoms in different layers of a stack are coupled together, and we have demonstrated the application of our idea to a structure Graphene layers. “

The Bath Research, published in Nature communicationis based on previous work on graphene ̵

1; a crystal characterized by thin layers of carbon atoms arranged in a honeycomb design. In 2018, scientists at the Massachusetts Institute of Technology (MIT) discovered that two layers of graphene, stacked and then twisted relative to each other by the “magic” angle of 1.1 °, create a material with superconducting properties. This was the first time that scientists made a superconducting material from pure carbon. However, these properties disappeared with the slightest change in the angle between the two graphene layers.

Since the discovery of MIT, scientists around the world have tried to apply this “stacking and twisting” phenomenon to other ultra-thin materials by joining two or more atomically different structures to form entirely new materials with unique properties.

“You can’t find materials in nature where every atomic layer is different,” said Dr. Mucha-Kruczynski. “Furthermore, two materials can normally only be put together in one way, because chemical bonds must form between layers. However, with materials like graphene, only the chemical bonds between atoms on the same plane are strong. The forces between planes – known as van der.” Waals interactions – are weak, and this allows layers of material to be twisted against each other. “

The challenge for scientists now is to make the process of discovering new, layered materials as efficient as possible. By finding a formula that they can use to predict the outcome when two or more materials are stacked, they can streamline their research tremendously.

In this area, Dr. Mucha-Kruczynski and his colleagues at Oxford University, Peking University and ELETTRA Synchrotron in Italy made a difference.

“The number of combinations of materials and the number of angles they can be rotated is too great to try in the lab, so what we can predict is important,” said Dr. Mucha-Kruczynski.

The researchers have shown that the interaction between two layers can be determined by examining a three-layer structure, where two layers are put together as you might find in nature, while the third is twisted. They used angle-resolved photoemission spectroscopy – a process in which strong light ejects electrons from the sample so that the energy and momentum of the electrons can be measured to gain insight into the properties of the material – to determine how strong two carbon atoms are at a given distance from each other are coupled. They have also shown that their result can be used to predict the properties of other stacks from the same layers, even if the twists between layers are different.

The list of known atomically thin materials like graphene is growing all the time. It already contains dozens of entries that have a variety of properties, from insulation to superconductivity, transparency to optical activity, brittleness to flexibility. The latest discovery provides a method for experimentally determining the interaction between layers of one of these materials. This is important for predicting the properties of more complicated stacks and for efficiently designing new devices.

Dr. Mucha-Kruczynski believes it could take 10 years for new stacked and twisted materials to find practical, everyday use. “It took graphene a decade to move from the lab to something useful in the usual sense. With a touch of optimism, I expect a similar schedule for new materials to apply,” he said.

Building on the results of his most recent study, Dr. Mucha-Kruczynski and his team are now working on twisted stacks of layers of transition metal dichalcogenides (a large group of materials with two very different types of atoms – a metal and a chalcogen). like sulfur). Some of these stacks have shown fascinating electronic behavior that scientists cannot yet explain.

“Because these are two radically different materials, these stacks are complicated to study,” said Dr. Mucha-Kruczynski. “However, we hope that over time we can predict the properties of different stacks and develop new multifunctional materials.”

Take the guesswork out of Twistronics

More information:
JJP Thompson et al., Determination of the interatomic coupling between two-dimensional crystals by means of angle-resolved photoemission spectroscopy, Nature communication (2020). DOI: 10.1038 / s41467-020-17412-0

Provided by the University of Bath

Quote: Physicists accelerate the search for revolutionary artificial atomic materials (2020, August 11), accessed on August 11, 2020 from https://phys.org/news/2020-08-physicists-revolutionary-artificial-atomic-materials.html

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