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Category: particle physics – Page 535

There’s a new form of matter out there and it’s called a supersolid. Born in the labs of researchers from the Massachusetts Institute of Technology (MIT), this new matter is seemingly a contradiction. The supersolid combines properties of solids and superfluids — or fluids with zero viscosity, thereby flowing without losing kinetic energy. Supersolids have previously been predicted by physicists, but have not been observed in a lab until now.

“It is counterintuitive to have a material which combines superfluidity and solidity,” says team leader Wolfgang Ketterle, the John D. MacArthur Professor of Physics at MIT and 2001 Noble laureate. “If your coffee was superfluid and you stirred it, it would continue to spin around forever.” Their research was published in the journal Nature.

To develop this seemingly contradictory form of matter, Ketterle’s team manipulated the motion of atoms in a superfluid state of dilute gas, called a Bose-Einstein condensate, or BEC. Ketterle co-discovered BEC, which won him his Noble prize in physics. “The challenge was now to add something to the BEC to make sure it developed a shape or form beyond the shape of the ‘atom trap,’ which is the defining characteristic of a solid,” Ketterle explained.

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A proton’s mass is more than just the sum of its parts. And now scientists know just what accounts for the subatomic particle’s heft.

Protons are made up of even smaller particles called quarks, so you might expect that simply adding up the quarks’ masses should give you the proton’s mass. However, that sum is much too small to explain the proton’s bulk. And new, detailed calculations show that only 9 percent of the proton’s heft comes from the mass of constituent quarks. The rest of the proton’s mass comes from complicated effects occurring inside the particle, researchers report in the Nov. 23 Physical Review Letters.

Quarks get their masses from a process connected to the Higgs boson, an elementary particle first detected in 2012 (SN: 7/28/12, p. 5). But “the quark masses are tiny,” says study coauthor and theoretical physicist Keh-Fei Liu of the University of Kentucky in Lexington. So, for protons, the Higgs explanation falls short.

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Engineers know that tiny, super-fast objects can cause damage to spacecraft, but it’s been difficult to understand exactly how the damage happens because the moment of impact is incredibly brief. A new study from MIT seeks to reveal the processes at work that produce microscopic craters and holes in materials. The hope is that by understanding how the impacts work, we might be able to more durable materials.

Accidental space impacts aren’t the only place these mechanisms come into play. There are also industrial applications on Earth like applying coatings, strengthening metallic surfaces, and cutting materials. A better understanding of micro-impacts could also make these processes more efficient. Observing such impacts was not easy, though.

For the experiments, the MIT team used tin particles about 10 micrometers in diameter accelerated to 1 kilometer per second. They used a laser system to launch the projectile that instantly evaporates a surface material and ejects the particles, ensuring consistent timing. That’s important because the high-speed camera pointed at the test surface (also tin) needed specific lighting conditions. At the appointed time, a second laser illuminated the particle allowing the camera to follow the impact at up to 100 million frames per second.

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The experimental investigation of ultracold quantum matter makes it possible to study quantum mechanical phenomena that are otherwise inaccessible. A team led by the Innsbruck physicist Francesca Ferlaino has now mixed quantum gases of two strongly magnetic elements, erbium and dysprosium, and created a dipolar quantum mixture.

A few years ago, it seemed unfeasible to extend the techniques of atom manipulation and deep cooling in the ultracold regime to many-valence-electron atomic species. The reason is the increasing complexity in the atomic spectrum and the unknown scattering properties. However, a team of researchers, led by Ben Lev at Stanford University and an Austrian team directed by Francesca Ferlaino at the University of Innsbruck demonstrated degeneracy of rare-earth species. Ferlaino’s group focused the on and developed a powerful, yet surprisingly simple approach to produce a Bose-Einstein condensate.

“We have shown how the complexity of atomic physics can open up new possibilities,” says Ferlaino. Magnetic species are an ideal platform to create dipolar quantum matter, in which particles interact with each other via a long-range and orientation dependent interaction as little quantum magnets.

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Researchers have developed catalysts that can convert carbon dioxide—the main cause of global warming—into plastics, fabrics, resins, and other products.

The electrocatalysts are the first materials, aside from enzymes, that can turn carbon dioxide and water into carbon building blocks containing one, two, three, or four carbon atoms with more than 99 percent efficiency.

Two of the products—methylglyoxal (C3) and 2,3-furandiol (C4)—can be used as precursors for plastics, adhesives, and pharmaceuticals. Toxic formaldehyde could be replaced by methylglyoxal, which is safer.

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