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Nathaniel Gabor is an associate professor of physics at UC Riverside. Credit: ICRA.
When two atomically thin two-dimensional layers are stacked one on the other and one layer is rotated relative to the second layer, they begin to produce patterns – familiar moire patterns – that no layer can generate alone and that facilitate the passage of light and electrons, allowing materials that exhibit unusual phenomena. For example, when two layers of graphene are superimposed and the angle between them is 1.1 degrees, the material becomes a superconductor.
"It's a bit like going past a vineyard and looking out the rows of vineyards from the windows – from time to time you do not see rows anymore because you look straight down a row," he said. said Nathaniel Gabor, an associate professor in the Department of Physics and Astronomy at the University of California, Riverside. "It looks like what happens when two atomic layers are stacked on top of each other, and at certain angles of torsion everything is allowed with energy. interesting possibilities of energy transfer. "
This is the future of new materials synthesized by twisting and stacking atomically thin layers, and is still at the stage of alchemy, Gabor added. To bring all these elements together under one roof, he and the physicist Justin CW Song of Nanyang Technological University in Singapore, proposed that this area of research be called "electronic quantum metamaterials" and has just published a perspective paper in Nature Nanotechnology.
"We emphasize the engineering potential of synthetic periodic matrices whose characteristic size is less than the wavelength of an electron.This technology allows electrons to be manipulated in ways that unusual, giving rise to a new range of synthetic quantum metamaterials with unconventional responses, "Gabor said.
Metamaterials are a class of materials designed to produce properties that do not occur naturally. Examples include optical masking devices and super-lenses similar to the Fresnel lens used by the headlights. Nature has also adopted such techniques – for example, in the unique coloring of butterfly wings – to manipulate photons that move through nanoscale structures.
"However, unlike photons that hardly interact with each other, electrons in structured sub-wavelength metamaterials are heavily charged and interact," Gabor said. "The result is an enormous variety of emerging phenomena and radically new classes of interacting quantum metamaterials."
Gabor and Song were invited by Nature Nanotechnology write a review article. But the couple chose to deepen and present fundamental physics that could largely explain the research on quantum electronic metamaterials. Instead, they wrote a perspective paper that looks at the current status of the field and discusses its future.
"Researchers, including our own labs, have explored a variety of metamaterials, but no one has yet given the name to this field," said Gabor, director of Quantum Materials' optoelectronics lab at UCR. "It is our intention to write this perspective.We are the first to codify the underlying physics.We express somehow the periodic table of this exciting new field.It is a Herculean task to codify all the work The ideas and the experiments have matured, and the literature shows that rapid progress has been made in the creation of quantum materials for electrons.It was time to put everything together and propose a roadmap for researchers to categorize future work. "
From this perspective, Gabor and Song collect early examples of electronic metamaterials and distill emerging design strategies for electronic control. They write that one of the most promising aspects of the new field occurs when electrons in sub-wavelength structure samples interact to exhibit unexpected emergent behavior.
"The behavior of superconductivity in twisted bilayer graphene that emerged was a surprise," Gabor said. "This shows, in a remarkable way, how electronic interactions and under-wavelength characteristics could be combined in quantum metamaterials to produce radically new phenomena." This is how a fascinating future is emerging for electronic metamaterials for many new jobs to come ".
Explore further:
Superconducting metamaterials trap quantum light
More information:
Justin C. W. Song et al. Quantum electronic metamaterials in van der Waals heterostructures, Nature Nanotechnology (2018). DOI: 10.1038 / s41565-018-0294-9
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