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Category: physics – Page 226

Three physicists in the Department of Physics and Astronomy at the University of Tennessee, Knoxville, together with their colleagues from the Southern University of Science and Technology and Sun Yat-sen University in China, have successfully modified a semiconductor to create a superconductor.

Professor and Department Head Hanno Weitering, Associate Professor Steve Johnston, and PhD candidate Tyler Smith were part of the team that made the breakthrough in fundamental research, which may lead to unforeseen advancements in technology.

Semiconductors are electrical insulators but conduct electrical currents under special circumstances. They are an essential component in many of the electronic circuits used in everyday items including mobile phones, digital cameras, televisions, and computers.

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When light falls on a material, such as a green leaf or the retina, certain molecules transport energy and charge. This ultimately leads to the separation of charges and the generation of electricity. Molecular funnels, so-called conical intersections, ensure that this transport is highly efficient and directed.

An international team of physicists has now observed that such conical intersections also ensure a directed energy transport between neighboring of a nanomaterial. Theoretical simulations have confirmed the . Until now, scientists had observed this phenomenon only within one molecule. In the long term, the results could help to develop more efficient nanomaterials for organic solar cells, for example. The study, led by Antonietta De Sio, University of Oldenburg, and Thomas Frauenheim, University of Bremen, Germany, was published in the current issue of the scientific journal Nature Nanotechnology.

Photochemical processes play a major role in nature and in technology: When molecules absorb light, their electrons transit to an excited state. This transition triggers extremely fast molecular switching processes. In the human eye, for example, the molecule rhodopsin rotates in a certain way after absorbing light and thus ultimately triggers an electrical signal—the most elementary step in the visual process.

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Florida’s Undefined Technologies claims it has managed to increase the thrust levels of ion propulsion systems to “unprecedented levels” with its “Air Tantrum” technology, enabling near-silent drones with no moving parts, that look like flying pallets.

All aircraft propulsion systems provide thrust by moving air or another propellant, and for the vast majority of drones that means some kind of fan or propeller spinning angled blades to push air through and create thrust in the opposite direction. Ionic propulsion, on the other hand, is entirely electromagnetic.

The process uses a high-voltage electric field to ionize the nitrogen and oxygen molecules in the air, liberating electrons to create, primarily, a lot of positively-charged nitrogen molecules. These are drawn toward a negatively-charged electrode, usually in the form of a flat screen grid, and as they accelerate, they bang into other air molecules and bump them in the same direction to create an ionic wind.

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In a new realm of materials, PhD student Thanh Nguyen uses neutrons to hunt for exotic properties that could power real-world applications.

Thanh Nguyen is in the habit of breaking down barriers. Take languages, for instance: Nguyen, a third-year doctoral candidate in nuclear science and engineering (NSE), wanted “to connect with other people and cultures” for his work and social life, he says, so he learned Vietnamese, French, German, and Russian, and is now taking an MIT course in Mandarin. But this drive to push past obstacles really comes to the fore in his research, where Nguyen is trying to crack the secrets of a new and burgeoning branch of physics.

“My dissertation focuses on neutron scattering on topological semimetals, which were only experimentally discovered in 2015,” he says. “They have very special properties, but because they are so novel, there’s a lot that’s unknown, and neutrons offer a unique perspective to probe their properties at a new level of clarity.”

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