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Category: particle physics – Page 192

If you could quickly predict the reactivity of a material in different scenarios using only its atomic-level geometry, you’d hold the golden ticket to finding application-specific catalytic materials. Some methods exist for making these predictions, but they require detailed knowledge about the arrangement of the atoms and are computationally expensive to perform and thus slow to run. Now Evan Miu and his colleagues at the University of Pittsburgh have developed a method that requires only information about the connectivity of the atoms, is computationally cheap, and is quick to run [1]. Their method accurately predicts how metal oxides interact with hydrogen in a reaction important to energy storage and catalysis.

Miu and the team hypothesized that they could predict a material’s reactivity using a single number that describes the so-called global connectivity of the system’s atoms. A material with a high global connectivity contains atoms that are, on average, bonded to more of their neighbors than does a system with a low value of this parameter. The researchers have used a similar concept to study reactivity for metal catalysts, but not for more complex structures, such as metal oxides.

To test their idea, the researchers examined—in different metal oxides—so-called hydrogen intercalation, a type of redox reaction that alters the host material’s properties. They found that they could use each oxide’s global connectivity to determine the strength of its hydrogen reactivity. The model-determined values for the various hydrogen-binding energies agree with experimental data and took mere seconds to obtain. The tool could thus allow scientists to rapidly develop and optimize novel materials to use in energy-storage applications.

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Scientists have developed a multifunctional metalens capable of structuring quantum emissions from single photon.

A photon is a particle of light. It is the basic unit of light and other electromagnetic radiation, and is responsible for the electromagnetic force, one of the four fundamental forces of nature. Photons have no mass, but they do have energy and momentum. They travel at the speed of light in a vacuum, and can have different wavelengths, which correspond to different colors of light. Photons can also have different energies, which correspond to different frequencies of light.

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There are several perfectly good reasons why water isn’t a popular medium for calligraphers to write in. Constantly shifting and swirling, it doesn’t take long for ink to diffuse and flow out of formation.

An ingenious ‘pen’ developed by the researchers from Johannes Gutenberg University Mainz (JGU) and the Technical University of Darmstadt in Germany, and Huazhong University of Science and Technology in China, could give artists a whole new medium to work with.

The new device is a tiny, 50 micron-wide bead made of a special material that exchanges ions in the liquid, creating zones of relatively low pH. Traces of particles suspended in the water are then drawn to the acidic solution. Drawing out that zone can create persistent, ‘written’ lines.

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Almost a century ago, physicists Satyendra Nath Bose and Albert Einstein predicted a theoretical state of matter in which individual particles would, at extremely cold temperatures and low densities, condense into an indistinguishable whole. These so-called Bose-Einstein condensates (BECs) would offer a macroscopic view into the microscopic world of quantum mechanics. In 1995, theoretical BECs became an experimental reality, which garnered the physicists who created them a Nobel Prize. Labs around the world— and even in space —have been creating them ever since.

All of the BECs created so far to ask fundamental questions about quantum mechanics have been made from atoms. It has proven much harder to make molecules cold enough to approach a BEC state, which hover fractions of a degree above absolute zero, and to keep the molecules stable long enough to conduct experiments.

“For twenty years, there have been proposals about what you could do with stable ultracold molecules, but it has been tough on the experimental side because the lifetime of molecular samples has been short,” said Columbia physicist Sebastian Will, whose lab specializes in creating ultracold atoms and molecules.

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Never let it be said that scientists don’t have an eye for the sublime.

Encoding and deciphering a Chinese symbol for duality and harmony into the quantum states of two entangled photons, physicists recently demonstrated the superior efficiency of a new analytical technique.

Researchers from the Sapienza University of Rome and the University of Ottawa in Canada used a method similar to a popular holographic technique to quickly and reliably measure information of a particle’s position.

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Quantum technology’s future rests on the exploitation of fascinating quantum mechanics concepts—such as high-dimensional quantum states. Think of these states as basic ingredients of quantum information science and quantum tech. To manipulate these states, scientists have turned to light, specifically a property called orbital angular momentum (OAM), which deals with how light twists and turns in space. Here’s a catch: making super bright single photons with OAM in a deterministic fashion has been a tough nut to crack.

Now, enter (QDs), tiny particles with big potential. A team of researchers from Sapienza University of Rome, Paris-Saclay University, and University of Naples Federico II combined the features of OAM with those of QDs to create a bridge between two cutting-edge technologies.

Their results are published in Advanced Photonics.

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The Large Hadron Collider (LHC) is best known for the 2012 discovery of the Higgs boson, which was made by smashing together high-energy protons (see Collection: The History of Observations of the Higgs Boson). But protons are not the only particles accelerated by the collider, and some studies call for colliding much heavier objects. Now a team working on the LHC’s ALICE experiment has collided lead nuclei to study an exotic particle called a hypertriton [1]. The result could help researchers reduce errors in models of the structure of neutron stars.

A hypertriton is a tritium nucleus in which one neutron has been replaced with a lambda hyperon, a heavier particle with a quark configuration of up-down-strange rather than up-down-down. Researchers have long known the energy it takes to bind tritium’s proton and two neutrons. But it was unclear how that energy changed with the neutron–lambda hyperon switch.

The ALICE Collaboration turned to lead–lead collisions to answer this question because these collisions produce hypertritons in much greater numbers than proton–proton ones do. A hypertriton quickly decays into a helium-3 nucleus and a pion, with the decay time and the energy of the decay products depending on the binding energy between the lambda hyperon and the hypertriton core.

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Active particles can form two-dimensional solids that are different from those formed by nonmotile particles, showing long-range crystalline order accompanied by giant spontaneous deformations.

If you compress a liquid slowly enough at low temperatures, it will freeze into an ordered solid: a crystal. Or at least that’s what we’re used to seeing in three dimensions. If you instead consider particles confined to a two-dimensional (2D) plane, the outcome is quite different. For equilibrium systems, a 2D solid stabilizes into a structure that lacks long-range order—it becomes less ordered further away from a central lattice site. The behavior of systems far from equilibrium, such as self-propelled particles, remains, however, an open question. In a numerical study of bacteria-like particles, Xia-qing Shi of Soochow University in China and his colleagues now show that active crystals follow a slightly different set of rules than their nonmotile counterparts [1]. Like 2D equilibrium crystals, 2D active systems stabilize into an ordered solid-like phase but with extremely large particle fluctuations around the configuration of a perfect crystal lattice.

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