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Category: particle physics – Page 7

Mostly empty foam overturns assumptions of electron beam stopping

When physicists fire beams of fast electrons at materials, they often need to know exactly how much energy those electrons will lose as they travel through. Through new research published in Physical Review Letters, a team led by Ke Jiang at Shenzhen Technology University in China has found that porous, mostly empty foam materials can stop high-current electron beams far more effectively than denser materials—overturning many previous assumptions about how these beams interact with solid materials.

When a beam of electrons travels through a solid, its energy is lost through collisions with the atoms and electrons already present in the material. But when electron beams carry extremely intense currents, driving electrons to travel close to the speed of light, individual collisions are no longer the dominant factor.

Instead, the beam generates powerful electromagnetic fields as it moves, which shape how the beam propagates and loses energy. In fields ranging from nuclear fusion to studies of planetary interiors, it is often crucial for physicists to manage this energy loss as tightly as possible.

Atomic bands in two transition metal dichalcogenides hint at long-theorized quantum state

Insulators are materials in which electrons cannot move freely. Past theoretical studies predicted the existence of an unusual insulating state dubbed obstructed atomic insulator (OAI), in which electrons are localized inside a crystal, while their centers of charge lie in empty spaces between atoms, rather than on the atoms themselves.

Two independent research teams, one at Princeton University and Donostia International Physics Center (DIPC), and the other at Columbia University recently observed signatures of this long-theorized quantum state in two different transition metal dichalcogenides, niobium diselenide (NbSe₂) and tungsten diselenide (WSe₂). Their papers, both of which were published in Nature Physics, could open new possibilities for the study of topological quantum phenomena.

Dual spacecraft capture both hemispheres of interstellar comet 3I/ATLAS at once

The Southwest Research Institute-led Ultraviolet Spectrograph (UVS) instruments aboard ESA’s Jupiter Icy Moons Explorer (Juice) spacecraft and NASA’s Europa Clipper made unique observations of interstellar comet 3I/ATLAS in late 2025. SwRI leads the UVS instruments on both spacecraft, simultaneously imaging both hemispheres of the comet and detecting the comet’s ultraviolet emissions.

Only the third recognized interstellar object, 3I/ATLAS, entered our solar system in July of 2025.

“As the comet passed between Juice and Europa Clipper, we were able to informally coordinate observations between the two spacecraft,” said Dr. Kurt Retherford, the principal investigator of Juice-UVS and Europa-UVS. “Crucially, we observed hydrogen, oxygen and carbon emissions. These elements are produced when gases escaping the comet’s nucleus break apart into atoms when exposed to sunlight.”

Quantum geometry provides theoretical limits on measurable properties of solids

Two RIKEN physicists have established new theoretical limits for experimentally measurable quantities by viewing solids through a lens of quantum geometry. Their results shed light both on the physics of solids and on quantum mechanics.

The usual approach to studying a solid in physics is to consider all the interactions acting between its atoms or molecules and then use the laws of quantum mechanics to determine the solid’s properties. But a new methodology involves considering the “quantum geometry” of a solid. It entails studying the geometric structures that arise not in physical space, but in the space of quantum states.

One of the key concepts in this approach is the quantum geometric tensor—a matrix that contains information about the distances and curvatures of quantum states.

3D atomic rearrangement creates 40,000 quantum defects in 40 minutes

It’s been 37 years since scientists first demonstrated the ability to move single atoms, suggesting the possibility of designing materials atom by atom to customize their properties. Today there are several techniques that allow researchers to move individual atoms in order to give materials exotic quantum properties and improve our understanding of quantum behavior.

But existing techniques can only move atoms across the surface of materials in two dimensions. Most also require painstakingly slow processes and high-vacuum, ultracold lab conditions.

Now a team of researchers at MIT, the Department of Energy’s Oak Ridge National Laboratory, and other institutions has created a way to precisely move tens of thousands of individual atoms within a material in minutes at room temperature. The approach uses a set of algorithms to carefully position an electron beam at specific locations of a material, then scan the beam to drive atomic motions.

AI surrogate accelerates nonlinear optics simulations by orders of magnitude

Simulating the nonlinear optical physics that underlies ultrafast laser systems is computationally demanding—a practical bottleneck in settings that require rapid feedback. A study by researchers at Stanford University, University of California, Los Angeles (UCLA), and SLAC National Accelerator Laboratory introduces a deep learning surrogate that delivers orders-of-magnitude acceleration over conventional simulation methods, while maintaining high fidelity across a challenging range of pulse shapes.

The work centers on second-order nonlinear optics (χ² processes), in which light waves exchange energy inside specially engineered crystals to generate new frequencies and tailored pulse shapes. In particle accelerator facilities, these processes play a key role. At SLAC’s upgraded Linac Coherent Light Source (LCLS-II), infrared laser pulses are first to green light and then to ultraviolet (UV). The UV pulse strikes a cathode to liberate an electron bunch that is subsequently accelerated and modulated to produce intense X-ray pulses. The temporal shape of the UV pulse directly influences the properties of that electron bunch—and ultimately the quality of the X-rays available for science.

A surrogate model for the nonlinear χ² frequency conversion step at the heart of this process is reported in Advanced Photonics.

Atoms vibrate on circular paths—with an unexpected twist

An international team of researchers, including scientists from HZDR and Fritz Haber Institute of the Max Planck Society, for the first time directly observed how angular momentum is transferred and conserved within a crystal lattice. Using intense terahertz laser pulses, the researchers were able to selectively control these processes, which unveiled a surprising effect: During the angular momentum transfer, the direction of rotation reverses—caused by the rotational symmetry of the material.

The results, published in Nature Physics, provide new insights into the foundation of magnetism and open up possibilities for tailored control of quantum materials.

Conserved quantities such as energy, momentum, and angular momentum determine the fundamental laws of nature. In a closed system, these quantities are always conserved: they cannot be created or destroyed, only transformed or transferred. While angular momentum is familiar in everyday life through rotating carousels or riding a bicycle, it plays a central role at the quantum level—for example, as the fundamental origin of magnetism.

How temperature changes light: New model could guide smarter LEDs, sensors and photonic devices

Technion researchers have developed, for the first time, a comprehensive physical model explaining how the properties of a radiating material, including absorption, emission, and quantum efficiency, affect the fundamental characteristics of the light it emits as a function of temperature. In essence, the emitted light changes its color, intensity, and randomness according to the material’s properties and its temperature. The discovery was published in Optica and opens new possibilities for designing advanced light sources, optical sensors, and thermally based photonic systems.

The research was led by M.Sc. student Tomer Bar-Lev and Prof. Carmel Rotschild from the Faculty of Mechanical Engineering and the Russell Berrie Nanotechnology Institute at the Technion. According to the researchers, the central phenomenon examined in this work is photoluminescence, a process in which a material emits light in response to incident illumination. In this phenomenon, light particles (photons) are absorbed by the material and re-emitted, forming the basis of many technologies, including LED lighting and optical sensors.

The Technion researchers demonstrated that the influence of fundamental physical laws formulated more than a century ago is far broader than previously thought.

In Quantum Gravity, the Cosmological Constant May Behave Similar To The Quantum Hall Effect

So why not do the same thing for a gravitational field? Well, it turns out that quantum renormalization only works for Euclidean space. In general relativity, the mass-energy of a system warps space and time. So all those quantum fluctuations curve spacetime, and curved spacetime induces even more virtual particles, which warp space even more… oh no! It all breaks down, and we can’t quantize gravitational fields the way we quantize the other fundamental forces.

Problems like these have led some researchers to develop a model known as loop quantum gravity. Rather than trying to calculate the behavior of quantum particles in a timey-wimey background, why not treat the entire mass-energy-spacetime structure as a single quantum system? It’s like imagining the Universe within an unseen background that is Euclidean. This way the problem of renormalization can be overcome in many cases. One case where it doesn’t work well is the cosmological constant. In most cosmological models, the cosmological constant is what drives cosmic expansion. Since it is a universal dark energy field, it amplifies the loop quantum gravity sums, and once again the whole thing diverges. You can handle this by fixing the cosmological constant to a specific value, but that isn’t really a solution to the problem. It’s the cosmology equivalent of ignoring the engine light in your car…

A new study finds this might not be too bad after all. In it, the authors demonstrate an interesting similarity between the cosmological constant in loop quantum gravity and the quantum Hall effect in standard quantum theory.

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