Using short laser pulses, researchers have imaged the exact moment an ammonia molecule bends and sheds a hydrogen atom.
Category: particle physics – Page 2
Imaging technique captures ultrafast electron and atom dynamics in chemical reactions
During chemical reactions, atoms in the reacting substances break their bonds and re-arrange, forming different chemical products. This process entails the movement of both electrons (i.e., negatively charged particles) and nuclei (i.e., the positively charged central parts of atoms). Valence electrons are shared and re-arranged between different atoms, creating new bonds.
The movements of electrons and nuclei during chemical reactions are incredibly fast, in many cases only lasting millionths of a billionth of a second (i.e., femtoseconds). Yet reliably tracking and understanding these movements could help to shed new light on how specific molecules are formed, as well as on the underpinnings of quantum mechanical phenomena.
Researchers at Shanghai Jiao Tong University recently introduced a new approach to observe chemical reactions as they unfold, precisely tracking the movement of electrons and atomic nuclei as a molecule breaks apart. This strategy, outlined in a paper published in Physical Review Letters, was successfully used to image the photodissociation of ammonia (NH₃), the process in which a NH₃ molecule absorbs light and breaks down into smaller pieces.
Understanding the unusual chirality-driven anomalous Hall effect via scattering theory
A new framework for understanding the nonmonotonic temperature dependence and sign reversal of the chirality-related anomalous Hall effect in highly conductive metals has been developed by scientists at Science Tokyo. This framework provides a clear picture of the unusual temperature dependence of chirality-driven transport phenomena, forming a foundation for the rational design of next-generation spintronic devices and magnetic quantum materials.
Magnetic materials exhibit a variety of intriguing properties during their magnetization process that reflect their magnetic states and excitations. These properties are studied by applying an external magnetic field to the material, producing the magnetization curve. Magnetic metals additionally demonstrate rich behavior in transport phenomena, referring to the flow of charge, heat, or spin under the influence of magnetic fields.
However, some of these behaviors are difficult to probe using the magnetization curve. The anomalous Hall effect (AHE) is one such effect. In the AHE, when an electric current passes through a magnetic metal, a voltage perpendicular to the current arises even in the absence of an external magnetic field. By contrast, in the traditional Hall effect, such a transverse voltage appears only when an external magnetic field is applied.
Honeycomb lattice sweetens quantum materials development
Researchers at the Department of Energy’s Oak Ridge National Laboratory are pioneering the design and synthesis of quantum materials, which are central to discovery science involving synergies with quantum computation. These innovative materials, including magnetic compounds with honeycomb-patterned lattices, have the potential to host states of matter with exotic behavior.
Using theory, experimentation and computation, scientists synthesized a magnetic honeycomb of potassium cobalt arsenate and conducted the most detailed characterization of the material to date. They discovered that its honeycomb structure is slightly distorted, causing magnetic spins of charged cobalt atoms to strongly couple and align.
Tuning these interactions, such as through chemically modifying the material or applying a large magnetic field, may enable the formation of a state of matter known as a quantum spin liquid. Unlike permanent magnets, in which spins align fixedly, quantum spins do not freeze in one magnetic state.
X-ray four-wave mixing captures elusive electron interactions inside atoms and molecules
Scientists at the X-ray free-electron laser SwissFEL have realized a long-pursued experimental goal in physics: to show how electrons dance together. The technique, known as X-ray four-wave mixing, opens a new way to see how energy and information flow within atoms and molecules. In the future, it could illuminate how quantum information is stored and lost, eventually aiding the design of more error-tolerant quantum devices. The findings are reported in Nature.
Much of the behavior of matter arises not from electrons acting alone, but from the ways they influence each other. From chemical systems to advanced materials, their interactions shape how molecules rearrange, how materials conduct or insulate and how energy flows.
In many quantum technologies —not least quantum computing—information is stored in delicate patterns of these interactions, known as coherences. When these coherences are lost, information disappears—a process known as decoherence. Learning how to understand and ultimately control such fleeting states is one of the major challenges facing quantum technologies today.
Overcoming symmetry limits in photovoltaics through surface engineering
A recent study carried out by researchers from EHU, the Materials Physics Center, nanoGUNE, and DIPC introduces a novel approach to solar energy conversion and spintronics. The work tackles a long-standing limitation in the bulk photovoltaic effect—the need for non-centrosymmetric crystals—by demonstrating that even perfectly symmetric materials can generate significant photocurrents through engineered surface electronic states. This discovery opens new pathways for designing efficient light-to-electricity conversion systems and ultrafast spintronic devices.
The work is published in the journal Physical Review Letters.
Conventional solar cells rely on carefully engineered interfaces, such as p–n junctions, to turn light into electricity. A more exotic mechanism—the bulk photovoltaic effect —can generate electrical current directly in a material without such junctions, but only if its crystal structure lacks inversion symmetry. This strict requirement has long restricted the search for practical materials.
Wormholes may not exist—we’ve found they reveal something deeper about time and the universe
Wormholes are often imagined as tunnels through space or time—shortcuts across the universe. But this image rests on a misunderstanding of work by physicists Albert Einstein and Nathan Rosen.
In 1935, while studying the behavior of particles in regions of extreme gravity, Einstein and Rosen introduced what they called a “bridge”: a mathematical link between two perfectly symmetrical copies of spacetime. It was not intended as a passage for travel, but as a way to maintain consistency between gravity and quantum physics. Only later did Einstein–Rosen bridges become associated with wormholes, despite having little to do with the original idea.
But in new research published in Classical and Quantum Gravity, my colleagues and I show that the original Einstein–Rosen bridge points to something far stranger—and more fundamental—than a wormhole.
Slowing down muon decay with short laser pulses
Muons are unstable subatomic particles that spontaneously and rapidly transform into other particles via a process known as electroweak decay. Altering the speed with which muons decay into other particles was so far deemed a challenging quest, requiring very strong electromagnetic fields that cannot be produced in conventional laboratory settings.
Researchers at the University of Plymouth, however, explored the possibility of influencing muon decay using short laser pulses. Their paper, published in Physical Review Letters, suggests that the behavior of muons can be altered when they pass through laser beams, an effect that could, in principle, also be achieved using laboratory lasers.
“Records are regularly being set for the highest intensity electromagnetic fields we can produce in the lab,” Dr. Ben King, co-author and Associate Professor of Theoretical Physics at the University of Plymouth, told Phys.org.
Hidden magma oceans could shield rocky exoplanets from harmful radiation
Deep beneath the surface of distant exoplanets known as super-Earths, oceans of molten rock may be doing something extraordinary: powering magnetic fields strong enough to shield entire planets from dangerous cosmic radiation and other harmful high-energy particles.
Earth’s magnetic field is generated by movement in its liquid iron outer core—a process known as a dynamo—but larger rocky worlds like super-Earths might have solid or fully liquid cores that cannot produce magnetic fields in the same way.
In a paper published in Nature Astronomy, University of Rochester researchers, including Miki Nakajima, an associate professor in the Department of Earth and Environmental Sciences, report an alternative source: a deep layer of molten rock called a basal magma ocean (BMO). The findings could reshape how scientists think about planetary interiors and have implications for the habitability of planets beyond our solar system.