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Category: particle physics

Beam-spin asymmetry study puts proton models to the test

Getting an up-close view of life at the cellular level can be as simple as placing onion skin under a microscope and adjusting the knobs. Peering deeper, into the heart of the atoms within, isn’t as easy. It requires peeling through layers of particle accelerator data to shed light on protons, neutrons and the subatomic processes at play.

This type of zoom doesn’t use a lens. Clarity is achieved by blending ultrafine physics measurements and theoretical predictions. Now, the first results from the KaonLT experiment at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility are adding a new level of detail in the quest to map out how the components of atomic nuclei are put together.

The study, published in the journal Physics Letters B, focuses on producing short-lived particles called mesons, which can provide important information about the particles and forces that form the proton.

Matching vibrations is all it takes to shut down superconductivity in a nearby crystal

The world is never really at rest. Even in a vacuum near ultracold temperatures where all classical motion should come to a halt, you’ll find quantum fluctuations. In thin, two-dimensional materials, these include random vibrations that can alter electromagnetic fields, a feature that theorists have posited could be quite useful for modifying materials.

“It’s a holy grail we’ve been searching for decades,” said Dmitri Basov, Higgins Professor of Physics at Columbia. “We believe we’ve found it.”

In a new paper published in Nature, Basov and 32 collaborators from 17 institutions came together to confirm that quantum fluctuations alone from the vacuum inside atom-thin layers of 2D materials can alter the properties of a larger nearby crystal—a theoretical possibility now experimentally realized for the first time.

New technique spots hidden defects to boost reliability of ultrathin electronics

Future devices will continue to probe the frontier of the very small, and at scales where functionality depends on mere atoms, even the tiniest flaw matters. Researchers at Rice University have shown that hard-to-spot defects in a widely used two-dimensional insulator can trap electrical charges and locally weaken the material, making it more likely to fail at lower voltages. The findings are published in Nano Letters.

“By showing practical ways to detect when and where these defects form, we help make future devices more reliable and repeatable,” said Hae Yeon Lee, an assistant professor of materials science and nanoengineering at Rice, who is a corresponding author on the study.

Building ultrathin electronics such as advanced transistors, photodetectors and quantum devices involves stacking sheets of different 2D materials on top of each other into “heterostructures.” Hexagonal boron nitride (hBN), prized for being atomically flat and chemically stable, is a common building block.

Energy loss triggers quantum thermal Hall-like effect at macroscopic scale

In many quantum materials—materials with unusual electrical and magnetic properties driven by quantum mechanical effects—electrons can organize themselves into Landau levels are essentially quantized energy states that form when charged particles move in a magnetic field.

This process, called Landau quantization, forces electrons into circular (i.e., cyclotron) motion. This motion ultimately produces evenly spaced Landau levels, which are known to underpin various physical phenomena, including the quantum Hall effect.

The quantum Hall effect is a quantum equivalent of the Hall effect that emerges in some two-dimensional (2D) materials at extremely low temperatures and under strong magnetic fields. This effect prompts electrical current to flow along the edges of a material with extremely low loss of energy.

A new, useful absorption limit for ultra-thin films

The applications of ultrathin, conductive films such as those made of graphene have many applications, but it’s been thought their efficacy is limited to absorbing only half of the incidental light at best. A research group in China has now shown that absorption can be as high as 82.8% at light grazing angles nearly parallel to the film. This could not only significantly improve design efficiencies but sheds light on light-matter interactions at sizes much lower than the light’s wavelength. Their work has been published in Physical Review Letters.

Graphene ultrathin films, as thin as one carbon atom (about 0.34 nanometers, 300,000 times thinner than a sheet of paper) have many applications: flexible and transparent electronics, energy storage and batteries, solar cells and photovoltaics, sensors and high-speed electronics and more, where they absorb light.

While such films allow for miniaturizing devices and reducing their weight, their extreme thinness has led to the characterization that they are limited to absorbing only half of the incoming light.

Rydberg atoms detect clear signals from a handheld radio

For the first time, a team of US researchers has used sensors containing highly excited Rydberg atoms to detect signals from an ordinary handheld radio. Through a careful approach to demodulating the incoming signals, Noah Schlossberger and colleagues at the National Institute of Standards and Technology (NIST) were able to recover audio encoded in multiple public radio channels, with promising implications for everyday uses in consumer electronics. The research has been published in Physical Review Applied.

In a Rydberg atom, a single electron is excited to an extremely high energy level, pushing it far from its host atom’s nucleus. From a distance, these atoms resemble a single electron orbiting a positively charged ion.

When any atom is exposed to an external electric field, the positions of its electrons’ energy levels shift through a process called the Stark effect. Yet in a Rydberg atom, the shift becomes far more pronounced, causing particularly striking changes in the spectral patterns produced when the atom is probed by a laser.

Major battery breakthrough paving way for EV upgrade

Chinese scientists have developed a lithium metal battery that boasts an energy density of more than 700 watt-hours per kilogram and stable performance at extremely low temperatures, marking a significant advancement in the production of high-energy batteries for electric vehicles. The research paper was published on Thursday in the science journal Nature.

Chen Jun, an academician of the Chinese Academy of Sciences and vice-president of Nankai University in Tianjin, was among the researchers who led the breakthrough. Chen said the team has replaced oxygen atoms with fluorine ones. It designed and synthesized novel fluorinated hydrocarbon solvent molecules, creating a new electrolyte system based on lithium-fluorine coordination.

A world first at the microscopic scale: Metamaterials that can shrink and expand on their own

Leiden physicists Daniela Kraft and Julio Melio have created soft structures that can take on different shapes without any external drive in their lab. They present their research on microscale metamaterials in Nature —a breakthrough that opens the door to smart, reconfigurable materials and microscopic robots.

“Metamaterials have completely changed the way we think about materials,” explains Professor of Experimental Physics Daniela Kraft. “In these systems, movements are no longer set by the material itself, but by the structure—the way particles are connected. We set out to create such functional structures at the microscopic scale. And we succeeded.”

A robust new telecom qubit identified in silicon

Quantum technologies are anticipated to transform computing, communication, and sensing by harnessing the unusual behavior of matter at the atomic scale. Translating quantum’s promise into practical devices will require physical systems that have desirable quantum properties and can be easily manufactured. Silicon, the material behind today’s computer chips, is highly attractive as a platform because it plays to the strengths of the trillion-dollar semiconductor industry that has already been built. Identifying quantum building blocks—qubits—in silicon is, therefore, an important frontier research area.

In a new study, researchers in UC Santa Barbara materials professor Chris Van de Walle’s Computational Materials Group identified a robust new qubit in silicon, called the CN center. The work is published in the journal Physical Review B.

Qubits can be based on atomic-scale defects in a crystal. A prototype example is the NV center, which consists of a nitrogen (N) atom sitting next to a vacancy (V, a missing carbon atom) in a diamond crystal. These defects can interact with both electrons and light, allowing them to emit single photons (quanta of light) that can transmit quantum information or be processed in quantum networks.

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