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Category: particle physics

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.

When heat flows backwards: A neat solution for hydrodynamic heat transport

When we think about heat traveling through a material, we typically picture diffusive transport, a process that transfers heat from high-temperature to low-temperature as particles and molecules bump into each other, losing kinetic energy in the process. But in some materials, heat can travel in a different way, flowing like water in a pipeline that—at least in principle—can be forced to move in a direction of choice. This second regime is called hydrodynamic heat transport.

Heat conduction is mediated by movement of phonons, which are collective excitations of atoms in solids, and when phonons spread in a material without losing their momentum in the process, you have phonon hydrodynamics.

The phenomenon has been studied theoretically and experimentally for decades, but is becoming more interesting than ever to experimentalists because it features prominently in materials like graphene, and could be exploited to guide heat flow in electronics and energy storage devices.

Five ways quantum technology could shape everyday life

The unveiling by IBM of two new quantum supercomputers and Denmark’s plans to develop “the world’s most powerful commercial quantum computer” mark just two of the latest developments in quantum technology’s increasingly rapid transition from experimental breakthroughs to practical applications.

There is growing promise of quantum technology’s ability to solve problems that today’s systems struggle to overcome, or cannot even begin to tackle, with implications for industry, national security and everyday life.

So, what exactly is quantum technology? At its core, it harnesses the counterintuitive laws of quantum mechanics, the branch of physics describing how matter and energy behave at the smallest scales. In this strange realm, particles can exist in several states simultaneously (superposition) and can remain connected across vast distances (entanglement).

Experiment relies on pulsars to probe dark matter waves

Dark matter is a type of matter that is predicted to make up most of the matter in the universe, yet it is very difficult to detect using conventional experimental techniques, as it does not emit, absorb, or reflect light. While some past studies gathered indirect hints of its existence, dark matter has never been directly observed; thus, its composition remains a mystery.

One hypothesis is that dark matter is made up of axionlike particles with an extremely low mass, broadly referred to as ultralight axionlike dark matter (ALDM). As these particles are exceedingly light, predictions suggest that they would behave more like waves than individual particles on a galactic scale.

The PPTA collaboration, a large team of researchers based at different institutes worldwide, applied a new approach to search for ALDM by cross-correlating polarization data of pulsars, neutron stars that spin rapidly and emit highly regular beams of radio waves. This approach, termed the “Pulsar Polarization Array (PPA),” entails measuring the polarization position angles of a series of pulsars and how they changed over time and with respect to pulsar spatial position.

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