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Category: particle physics – Page 3

A New Model for Particle Charging

As flour, plastic dust, and other powdery particles get blown through factory ducts, they become charged through contact with each other and with duct walls. To avoid discharges that could ignite explosions, ducts are metallic and grounded. Still, particles remain an explosive threat if they reach a silo while charged. The microphysics of contact charging is an active area of research, as is the quest to understand the phenomenon as it plays out on larger scales in dust storms, volcanic plumes, and processing plants. Now Holger Grosshans of the German National Metrology Institute in Braunschweig and his collaborators have developed a contact-charging model that can cope with particles and walls made of different materials [1]. What’s more, the model is compatible with computational approaches used to analyze large-scale turbulent flows.

The model treats particles’ acquisition of electric charge from each other and their surroundings as a stochastic process—one that involves some randomness. The resulting charge distributions depend on the amount of charge transferred per impact and other nanoscale parameters that would be tedious to measure for each system. Fortunately, Grosshans and his collaborators found that if they determined all parameters for one system in a controlled experiment, they could readily adjust the parameters to suit other systems.

To test their model, the researchers coupled it to a popular fluid-dynamics solver and simulated 300,000 polymer microparticles stirred by a turbulent flow while confined between four walls. The combination reproduced the complex charging patterns observed in lab experiments—and it did so efficiently: The charging model added less than 0.01% to the simulation’s computational cost.

A Laser Built for Nuclear Timekeeping

Researchers have designed and demonstrated an ultraviolet laser that removes a major bottleneck in the development of a nuclear clock.

Whereas ordinary atomic clocks keep time using transitions of electrons in atoms, a prospective nuclear clock would harness a transition between states of the nucleus. Compared with electronic transitions, nuclear ones are much less sensitive to environmental disturbances, which would potentially give nuclear clocks unprecedented precision and stability. Such devices could improve GPS systems and enable more sensitive probes of fundamental physics. The main hurdle has been that nuclear transitions are extremely difficult to drive controllably using existing laser technology. Now Qi Xiao at Tsinghua University in China and colleagues have proposed and realized an intense single-frequency ultraviolet laser that can achieve such driving for thorium-229 nuclei [1, 2]. Beyond timekeeping, the team’s laser platform could find uses across quantum information science, condensed-matter physics, and high-resolution spectroscopy.

For most nuclear transitions, the energy difference between the two states lies in the kilo-electron-volt to mega-electron-volt range. Consequently, such transitions are inaccessible to today’s high-precision lasers, which can deliver photons of typically a few electron volts in energy. A long-known exception is the transition between the ground state and first excited state of thorium-229 nuclei. Indirect measurements over the past 50 years have gradually pinned down that transition’s energy difference to only about 8.4 eV. As a result, this transition is being actively investigated as a candidate for developing a nuclear clock.

A familiar magnet gets stranger: Why cobalt’s topological states could matter for spintronics

The element cobalt is considered a typical ferromagnet with no further secrets. However, an international team led by HZB researcher Dr. Jaime Sánchez-Barriga has now uncovered complex topological features in its electronic structure. Spin-resolved measurements of the band structure (spin-ARPES) at BESSY II revealed entangled energy bands that cross each other along extended paths in specific crystallographic directions, even at room temperature. As a result, cobalt can be considered as a highly tunable and unexpectedly rich topological platform, opening new perspectives for exploiting magnetic topological states in future information technologies.

The findings are published in the journal Communications Materials.

Cobalt is an elementary ferromagnet, and its properties and crystal structure have long been known. However, an international team has now discovered that cobalt hosts an unexpectedly rich topological electronic structure that remains robust at room temperature, revealing a surprising new level of quantum complexity in this material.

NOvA maps neutrino oscillations over 500 miles with 10 years of data

Neutrinos are very small, neutral subatomic particles that rarely interact with ordinary matter and are thus sometimes referred to as ghost particles. There are three known types (i.e., flavors) of neutrinos, dubbed muon, electron and tau neutrinos.

Interestingly, physicists discovered that as they travel, neutrinos can change flavor, which requires that neutrinos have a small, but not zero, mass. This phenomenon, known as neutrino oscillation, has been widely investigated in recent years, as studying it could help to infer the properties of neutrinos.

The NOvA experiment, a U.S.-based particle physics research endeavor, has been collecting data with two neutrino detectors that are far apart from each other, one located at the Fermi National Laboratory (Fermilab) in Illinois and the other at a facility in Northern Minnesota. In a recent paper, published in Physical Review Letters, the researchers involved in the NOvA experiment published some of the most precise neutrino oscillation measurements to date.

Physicists challenge a 200-year-old law of thermodynamics at the atomic scale

A long-standing law of thermodynamics turns out to have a loophole at the smallest scales. Researchers have shown that quantum engines made of correlated particles can exceed the traditional efficiency limit set by Carnot nearly 200 years ago. By tapping into quantum correlations, these engines can produce extra work beyond what heat alone allows. This could reshape how scientists design future nanoscale machines.

Two physicists at the University of Stuttgart have demonstrated that the Carnot principle, a foundational rule of thermodynamics, does not fully apply at the atomic scale when particles are physically linked (so-called correlated objects). Their findings suggest that this long-standing limit on efficiency breaks down for tiny systems governed by quantum effects. The work could help accelerate progress toward extremely small and energy-efficient quantum motors. The team published its mathematical proof in the journal Science Advances.

Traditional heat engines, such as internal combustion engines and steam turbines, operate by turning thermal energy into mechanical motion, or simply converting heat into movement. Over the past several years, advances in quantum mechanics have allowed researchers to shrink heat engines to microscopic dimensions.

A simple discovery is shaking the foundations of spintronics

A long-standing mystery in spintronics has just been shaken up. A strange electrical effect called unusual magnetoresistance shows up almost everywhere scientists look—even in systems where the leading explanation, spin Hall magnetoresistance, shouldn’t work at all. Now, new experiments reveal a far simpler origin: the way electrons scatter at material interfaces under the combined influence of magnetization and an electric field.

Myomaker and ether lipids cooperate to promote fusion-competent membrane states

This study identifies ether-linked phospholipids as modulators of Myomaker-mediated membrane fusion, revealing a lipid-centric perspective on the mechanisms driving myocyte fusion. Although we found no evidence of ceramidase activity for Myomaker, inhibiting sphingolipid biosynthesis enhanced fusion in both myocytes and BHK cells expressing Myomaker and Myomerger. These findings indicate that sphingolipids are not required for Myomaker function and may even act as antagonists of fusion. Lipidomic analyses under sphingolipid inhibition revealed an enrichment in ether lipids. Known for their fusogenic properties, these lipids were also enriched in Myomaker-containing lentiviral particles, indicating that membranes rendered fusion competent by Myomaker have higher concentrations of ether lipids. One possibility is that Myomaker may reside in, or help establish, lipid microdomains enriched in ether lipids. Functionally, increasing ether lipid levels, via Far1 overexpression or supplementation with the ether lipid precursor HG, was sufficient to induce Myomaker-dependent fusion even in the absence of Myomerger. Additionally, elevated ether lipid levels enhanced Myomaker’s localization to the plasma membrane and promoted externalization of PE and PS, hallmarks of membrane remodeling. Together, these findings suggest that ether lipids act as regulators of Myomaker activity and reveal a relationship between membrane lipid remodeling and Myomaker-mediated fusion.

Our work indicates that specific lipid classes, beyond their general fusogenic characteristics, can regulate protein-driven cell-cell fusion. One possible explanation for the ability of ether lipids to induce fusion in the presence of Myomaker is that they simply increase the amount of protein on the plasma membrane. While we detected an increase in plasma membrane-associated Myomaker after elevation of ether lipids, alternative ways to increase levels of Myomaker on the membrane, such as inhibition of autophagy, did not induce fusion, indicating that increases in plasma membrane Myomaker are not sufficient to induce fusion. This suggests that ether lipids influence the activity of Myomaker through additional mechanisms. One can hypothesize that an elevation in ether lipids promotes hemifusion-to-fusion transition by compensating for Myomerger’s activity.

Current flows without heat loss in newly engineered fractional quantum material

A team of US researchers has unveiled a device that can conduct electricity along its fractionally charged edges without losing energy to heat. Described in Nature Physics, the work, led by Xiaodong Xu at the University of Washington, marks the first demonstration of a “dissipationless fractional Chern insulator,” a long-sought state of matter with promising implications for future quantum technologies.

The quantum Hall effect emerges when electrons are confined to a two-dimensional material, cooled to extremely low temperatures, and exposed to strong magnetic fields. Much like the classical Hall effect, it describes how a voltage develops across a material perpendicular to the direction of current flow. In this case, however, that voltage increases in discrete, or quantized steps.

Under even more extreme conditions, an exotic variant appears named the “fractional quantum Hall” (FQH) effect. Here, electrons no longer behave as independent particles but move collectively, giving rise to voltage steps that correspond to fractions of an electron’s charge. This unusual collective behavior unlocks a whole host of exotic properties, and has made such states particularly appealing for emerging quantum technologies.

Machine learning reveals hidden landscape of robust information storage

In a new study published in Physical Review Letters, researchers used machine learning to discover multiple new classes of two-dimensional memories, systems that can reliably store information despite constant environmental noise. The findings indicate that robust information storage is considerably richer than previously understood.

For decades, scientists believed there was essentially one way to achieve robust memory in such systems—a mechanism discovered in the 1980s known as Toom’s rule. All previously known two-dimensional memories with local order parameters were variations on this single scheme.

The challenge lies in the sheer scale of possibilities. The number of potential local update rules for a simple two-dimensional cellular automaton is astronomically large, far greater than the estimated number of atoms in the observable universe. Traditional methods of discovery through exhaustive search or hand-design are therefore impractical at this scale.

Anomalous magnetoresistance emerges in antiferromagnetic kagome semimetal

Researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences (CAS), in collaboration with researchers from the Institute of Semiconductors of CAS, revealed anomalous oscillatory magnetoresistance in an antiferromagnetic kagome semimetal heterostructure and directly identified its corresponding topological magnetic structures. The results are published in Advanced Functional Materials.

Antiferromagnetic kagome semimetals, characterized by a strong interplay of geometric frustration, spin correlations, and band topology, have emerged as a promising platform for next-generation antiferromagnetic topological spintronics.

In this study, the researchers fabricated an FeSn/Pt heterostructure based on an antiferromagnetic kagome semimetal. By breaking inversion symmetry at the interface, the researchers introduced and tuned the Dzyaloshinskii-Moriya interaction, enabling effective control of spin configurations in the FeSn layer.

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