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Category: particle physics

Solar Storm Unexpectedly Reduces Cosmic-Ray Flux

A solar storm hitting Earth appears to have reduced the amount of incoming high-energy cosmic rays, suggesting a new way of measuring solar activity.

Solar activity has a well-known impact on the flux of low-energy cosmic rays that strike Earth. Now researchers have detected a solar-storm-induced change in the flux of higher-energy cosmic rays [1]. Using data from a large detector array in China, the team measured a decrease—over several hours—in cosmic-ray showers coming from a particular direction in the sky. The timing of this anisotropy suggests that cosmic rays heading into the outward-moving storm were preferentially scattered by the storm’s magnetic fields. The results could lead to a new way to study the magnetic structures in solar storms.

The solar wind—the spray of charged particles continually emitted by the Sun—partially shields Earth and other planets from cosmic rays that stream into the Solar System from all directions. The wind contains magnetic fields that help deflect the high-energy protons and other particles that make up the cosmic rays. In 2024, when the wind was at the peak in its 11-year cycle, the flux of cosmic rays was down by about 0.5% compared to the average.

Metal hydride molecule trapped with laser light opens path to ultracold hydrogen

Controlling and trapping molecules, units of a substance consisting of two or more chemically bound atoms, with laser light is significantly more challenging than trapping individual atoms. This is because molecules exhibit more complex vibrational and rotational dynamics that make them more difficult to cool and trap.

In a paper published in Physical Review Letters, researchers at Columbia University and Indiana University Bloomington reported the effective cooling and trapping of calcium monohydride (CaH), a molecule consisting of a calcium atom and a hydrogen atom bound together.

This was achieved using a three-dimensional (3D) magneto-optical trap (MOT), a device that uses carefully arranged laser beams and magnetic fields to cool and confine particles.

Dog-bone design helps 2D nanoribbon transistors stay fast and efficient as widths shrink

Transistors, small semiconductor-based switches that control the flow of electricity, are central components of all electronic devices, from computers to smartphones, wearables, sensors and smart appliances. Over the past decades, electronics engineers have been continuously working to boost the speed and performance of transistors while also reducing their size.

A promising approach for miniaturizing transistors entails the use of two-dimensional (2D) semiconductors, materials that are only one or a few atoms thick. Despite their potential, most high-performing 2D transistors have so far been demonstrated using relatively wide channels, and it has remained unclear whether their performance can be preserved when the channels are made much narrower.

Researchers at Stanford University recently developed new compact transistors based on narrow strips of monolayer 2D semiconducting materials known as nanoribbons. These transistors, introduced in a paper published in Nature Nanotechnology, were found to perform remarkably well despite their small size, outperforming previously developed nanoribbon transistors based on the same 2D materials.

Clean crystal surface lets single molecules hit ultimate quantum limit

Scientists at the Max Planck Institute for the Science of Light (MPL) have developed a technique for interrogating molecules on surfaces with spectroscopic precision, thereby reaching the ultimate quantum limit for the first time. With their findings, published in Science, the researchers open new opportunities for the study of molecule-surface interactions and molecular quantum technologies.

Many optical quantum technologies rely on nanoscale objects, such as atoms or molecules, that interact strongly with light. These quantum emitters are used for generating single photons, storing quantum information and entanglement distribution, processes that find application in quantum communication and computation.

To investigate these emitters individually, researchers need to keep them in one place for a long time. This is usually achieved by either trapping them in a vacuum or placing them inside a bulk material. Quantum emitters located on a surface would create new opportunities to manipulate their functionalities by “touching them,” for example, with an atomically sharp tip, as is used in scanning tunneling microscopy (STM) and atomic force microscopy (AFM).

Trios of quantum particles form checkerboard layouts when particle density hits sweet spot

Trions form when three particles, like quarks or electrons, come together. This formation occurs in quantum particles in nuclear physics, semiconductors and magnets, and understanding its behavior can be challenging. Rice University’s Kaden Hazzard and his team recently developed a theory on how these formations occur and behave, which was published in Physical Review Letters.

“Our theory sheds light on how trions form and interact with each other,” said Hazzard, associate professor of physics and astronomy and corresponding author on the paper. “It predicts the strength of the interactions needed to form the trions, and that, after formation, they arrange themselves in a checkerboard pattern.”

If you imagine a space full of equal amounts of red, blue and yellow balls, a trion would form when a red, blue and yellow ball all stuck to each other, Hazzard explained. Once all the balls, or particles, are bound together, he was curious about how these trions would arrange themselves in space.

Scientists develop predictive roadmap to boost performance in next-gen spintronics

Chiral 2D metal halide perovskites (MHPs) are among the most promising materials for future technologies that exploit the spin of electrons in spin-based optoelectronics, or spintronics, but getting them to perform consistently has proven difficult. Now scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a data-driven approach that identifies and models key synthesis parameters to optimize their performance.

The difficulty stems in part from the sheer number of factors involved in making these materials. Although chiral 2D MHPs are low-cost and easy to fabricate as thin films, optimizing those films for optoelectronic technologies such as light-emitting diodes (LEDs) or photodetectors is a formidable challenge. Advanced spin-based optoelectronics use circularly polarized light to encode and transmit data. For several years, scientists have searched for ways to enhance these materials’ selectivity for circularly polarized light, but progress has been hampered by a reproducibility problem: Reported performance values for nominally the same material vary by more than two orders of magnitude across different laboratories.

A new study published in the journal Matter offers a roadmap for solving that problem. Scientist Carolin Sutter-Fella and her team at Berkeley Lab’s Molecular Foundry show how systematically tuning several “knobs” in the fabrication process—such as solvent choice, annealing temperature and film thickness—can reliably improve the material’s chiroptical properties, or its ability to interact with circularly polarized light.

Laser pulses capture unexplored polaronic states

In an international experiment, researchers observed Jahn–Teller polarons—quasiparticles that could play an important role in future ultrafast spintronic devices. These polarons emerged within the crystal lattice of cobalt oxide that had been activated by carefully tailored laser pulses.

When a cobalt oxide crystal is exposed to carefully tailored laser pulses, they induce specific local distortions of the crystal lattice that strongly affect the material’s structural, electrical and magnetic properties. The correlative experimental approaches that revealed these unexpected properties of cobalt oxide were carried out by a large international team of scientists from the University of Pavia (Italy), the Swiss Federal Institute of Technology Lausanne, the Paul Scherrer Institute (Switzerland), the University of Texas at Austin, the Massachusetts Institute of Technology and Northeastern University (U.S.). The theoretical description of the phenomenon, which made it possible to uncover the nature of the observed oscillations, was developed by physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow.

Chemical catalysts, battery electrodes, photovoltaic cells and semiconductor gas sensors—these are just some of the modern applications of cobalt oxide (Co₃O₄). Despite its simple chemical formula, the unit cell of its crystal lattice consists of 56 atoms: 24 cobalt and 32 oxygen. Depending on their position within the unit cell, the cobalt atoms exist here in two oxidation states.

3 Reasons Pilot Wave Theory is The Best Interpretation of Quantum Mechanics (And 3 Reasons It’s Not)

The pilot wave interpretation of quantum mechanics is probably a lot better than you think.

Pilot wave theory makes a bold claim: that it reproduces all the predictions of quantum mechanics while resolving nearly all of its infamously difficult conceptual issues.

And that claim is justified!

But if pilot wave theory is so good, why doesn’t anyone talk about it?

Here are 3 reasons why people should talk about pilot wave theory, but also 3 reasons why people don’t.
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Ultrafast X-rays allow researchers to ‘watch’ how molecules rearrange during a chemical reaction controlled by light

Since the 1980s, researchers have sought to use laser light to control chemical reactions relevant to photochemistry, catalysis and light-responsive materials. But this technique, known as coherent control, has a blind spot: There has been no way to directly see the molecules in these reactions as their structures rearrange.

Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory have imaged a coherently controlled chemical reaction for the first time. Their work, published in Physical Review A, uses ultrafast X-rays from the Linac Coherent Light Source (LCLS) to show in real time how atoms move in a molecule that was excited and manipulated with laser light.

“There are many challenges with controlling chemical reactions, but seeing is believing,” said study lead author Tom Hopper, assistant professor at the University of Central Florida who was a postdoctoral researcher at SLAC at the time of the study. “If you can see something directly, it opens up a new level of control.”

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