Rutgers University-New Brunswick researchers have discovered a new class of materials -- called intercrystals -- with unique electronic properties that could power future technologies.
Intercrystals exhibit newly discovered forms of electronic properties that could pave the way for advancements in more efficient electronic components, quantum computing and environmentally friendly materials, the scientists said.
As described in a report in the science journal Nature Materials, the scientists stacked two ultrathin layers of graphene, each a one-atom-thick sheet of carbon atoms arranged in a hexagonal grid. They twisted them slightly atop a layer of hexagonal boron nitride, a hexagonal crystal made of boron and nitrogen. A subtle misalignment between the layers that formed moiré patterns -- patterns similar to those seen when two fine mesh screens are overlaid -- significantly altered how electrons moved through the material, they found.
"Our discovery opens a new path for material design," said Eva Andrei, Board of Governors Professor in the Department of Physics and Astronomy in the Rutgers School of Arts and Sciences and lead author of the study. "Intercrystals give us a new handle to control electronic behavior using geometry alone, without having to change the material's chemical composition."
By understanding and controlling the unique properties of electrons in intercrystals, scientists can use them to develop technologies such as more efficient transistors and sensors that previously required a more complex mix of materials and processing, the researchers said.
"You can imagine designing an entire electronic circuit where every function -- switching, sensing, signal propagation -- is controlled by tuning geometry at the atomic level," said Jedediah Pixley, an associate professor of physics and a co-author of the study. "Intercrystals could be the building blocks of such future technologies.
"The discovery hinges on a rising technique in modern physics called "twistronics," where layers of materials are contorted at specific angles to create moiré patterns. These configurations significantly alter the behavior of electrons within the substance, leading to properties that aren't found in regular crystals.
The foundational idea was first demonstrated by Andrei and her team in 2009, when they showed that moiré patterns in twisted graphene dramatically reshape its electronic structure. That discovery helped seed the field of twistronics.
Electrons are tiny particles that move around in materials and are responsible for conducting electricity. In regular crystals, which possess a repeating pattern of atoms forming a perfectly arranged grid, the way electrons move is well understood and predictable. If a crystal is rotated or shifted by certain angles or distances, it looks the same because of an intrinsic characteristic known as symmetry.
The researchers found the electronic properties of intercrystals, however, can vary significantly with small changes in their structure. This variability can lead to new and unusual behaviors, such as superconductivity and magnetism, which aren't typically found in regular crystals. Superconducting materials offer the promise of continuously flowing electrical current because they conduct electricity with zero resistance.
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