New solution to an old magnetism puzzle

How are superconductivity and magnetism connected? A puzzling relation between magnetism and superconductivity in a quantum material has lingered for decades – now a study from TU Wien offers a surprising new explanation.

Vienna University of Technology

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Aline Ramires

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Credit: TU Wien

Some materials conduct electricity without any resistance when cooled to very low temperatures. This phenomenon, known as superconductivity, is closely linked to other important material properties. However, as new work by physicist Aline Ramires from the Institute of Solid State Physics at TU Wien now shows: in certain materials, superconductivity does not generate exotic magnetic properties, as was widely assumed. Instead, it merely makes an unusual form of magnetism experimentally observable – so-called altermagnetism.

Back to the future: time-reversal symmetry

How can one tell whether a film is running forwards or backwards? Many physical phenomena make no distinction between forward and reversed time. Magnetism, however, does: if a particle is deflected to the right in a magnetic field, then running time backwards would make it appear to be deflected to the left. In such cases, physicists speak of broken time reversal symmetry. This symmetry breaking can also occur in a subtle, quantum-mechanical way, for example in the quantum states of particles in certain materials. Almost always, it is a clear indication that magnetic effects are at work.

This was how a series of experimental results in different materials had been interpreted in the past: exactly below the temperature at which superconductivity sets in, certain exotic phenomena suddenly became visible. The conclusion seemed obvious – the superconductivity itself must be exotic, producing magnetism and breaking time reversal symmetry precisely at the moment it emerges. 

“Signs of broken time reversal symmetry were observed, for example, in the material strontium ruthenate (Sr₂RuO₄), but also in certain layered materials,” says Aline Ramires. “At first, everything seemed to make sense if one assumed a special, chiral form of superconductivity capable of generating magnetic effects. But the more experimental results accumulated, the more puzzling the picture became.”

New findings strongly suggest that superconducting strontium ruthenate should not, in fact, produce such magnetic effects at all. Other experiments even detected magnetic signatures above the critical temperature – that is, in a regime where superconductivity does not yet exist. “It was clear that something did not add up, but no one could explain these strange contradictions,” says Ramires.

Altermagnetism – an exotic form of magnetism

Ramires now shows that these puzzles can be traced back to an unusual type of magnetism that has only been identified in recent years and is known as altermagnetism. In conventional ferromagnetism, all participating electrons align their magnetic moments (their spins) in the same direction.

In antiferromagnetism, the opposite happens: neighboring spins point in opposite directions and cancel each other out on large length scales. “In altermagnetism, neighboring spins also point in opposite directions, but the spatial arrangement of one spin species is not exactly equivalent to that of the other,” explains Ramires. “As a result, altermagnetic materials behave in fundamentally different ways.”

Symmetry is the key

In certain materials, altermagnetism can exist both above and below the superconducting transition temperature and break time-reversal symmetry. However, the characteristic signatures by which condensed-matter physicists normally detect such symmetry breaking can remain hidden if the material possesses specific internal symmetries.

“If the atoms in a material are arranged in a particular symmetric way, certain effects are not visible – for example the Kerr effect, a change in the optical properties of a material that is regarded as a typical signature of broken time-reversal symmetry,” says Ramires. “When superconductivity sets in, some of these spatial symmetries can be broken – and this makes the previously hidden effects measurable.”

The conclusion is clear: superconductivity is not responsible for creating magnetism in these materials. The materials are magnetic all along – they are altermagnets. But in some cases, the internal symmetry of a material must be broken before the consequences of this altermagnetism can be observed. Where researchers had long suspected a magnetic ‘threshold’, the magnetism itself does not change at all – only its observable effects suddenly become visible.

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Journal

Physical Review Research

DOI

10.1103/jr65-4273 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

From pure to mixed: Altermagnets as intrinsic symmetry-breaking indicators

 

From sea to soil: Molecular changes suggest how algae evolved into plants

Early marine algae adapted their light-harvesting systems for weak blue-green light, suggesting how photosynthesis evolved

Osaka Metropolitan University

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Primitive green algae in aquatic environments use a distinct light-harvesting complex called Lhcp, which differs from the LHCII found in land plants, suggesting an evolutionary transition that occurred in photosynthetic systems as plants moved from water to land.

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Credit: Osaka Metropolitan University

Before plants evolved, vegetative life consisted of primitive green algae living in the sea. Like plants, these algae survived by performing photosynthesis, turning sunlight into energy. However, little light reaches the ocean where algae live; therefore, they evolved specialized organs to grab what little is available.

Among these tiny ocean algae are prasinophytes, which are among the earliest photosynthetic life forms on Earth. Like all photosynthetic organisms, they rely on a pigment–protein complex called LHC to capture sunlight. How efficiently LHC performs photosynthesis in different environments depends on the pigments bound to it.

A research team including Associate Professor Ritsuko Fujii of the Graduate School of Science at Osaka Metropolitan University used cryo-electron microscopy to look at the three-dimensional structure and function of Lhcp, a unique prasinophyte LHC, from the microscopic alga Ostreococcus tauri. The team compared their results to LHCII, which is found in terrestrial plants.

They found that the basic design of the protein scaffold was similar, but there were structural differences in pigment binding and protein loops that affect how Lhcp absorbs light and transfers energy. Unlike the plant’s light-harvesting complex, Lhcp’s trimer architecture is stabilized by both pigment–pigment and pigment–protein interactions, especially involving a unique carotenoid arranged at the interface between subunits.

“The carotenoid stabilizes the structure and improves the efficiency of light adsorption of blue-green light, which is abundant in the deep-sea environment,” Professor Fujii explained.

Their results showed that Lhcp includes structures unique to the algae despite sharing some structural and functional features with LHCII. These similarities and differences may be key changes that enabled plants to leave the oceans and colonize the land.

“Understanding this molecular foundation can be used to uncover why, when, and how land plants selected LHCII over Lhcp during their evolutionary process,” Professor Fujii added. “This may be key to understanding this important evolution event.”

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About OMU

Established in Osaka as one of the largest public universities in Japan, Osaka Metropolitan University is committed to shaping the future of society through the “Convergence of Knowledge” and the promotion of world-class research. For more research news, visit https://www.omu.ac.jp/en/ and follow us on social media: X, Facebook, Instagram, LinkedIn.

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Journal

Communications Biology

DOI

10.1038/s42003-025-08977-x 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Distinctive and functional pigment arrangements in Lhcp, a prasinophyte-specific photosynthetic light-harvesting complex

 

A hearing test for the world’s rarest sea turtle

Little is known about how sensitive the Kemp’s ridley sea turtle is to human noises.

American Institute of Physics

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Kemp’s ridley sea turtles are among the most endangered sea turtles on the planet, residing in the highly trafficked eastern and Gulf coasts of North America. Understanding how the noise produced by human activities affects them can help inform conservation efforts.

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Credit: Instigator/Shanna Stawicki Photography

WASHINGTON, Feb. 3, 2026 — Kemp’s ridley sea turtles are among the most endangered species of sea turtles in the world. They reside along the east and Gulf coasts of North America, alongside some of the world’s most active shipping lanes. While the threats from fishing, pollution, and vessel collisions are well understood, it is less clear how disruptive human-caused noise is to their survival.

In JASA, published on behalf of the Acoustical Society of America by AIP Publishing, researchers from Duke University Marine Laboratory, the National Oceanic and Atmospheric Administration, and North Carolina State University evaluated the hearing sensitivity of a group of Kemp’s ridley turtles to understand their vulnerability to human-caused noise.

“They face a variety of threats, including accidental capture in fishing gear, vessel strikes, ingestion of plastic debris, and degradation of nesting beaches and coastal habitat,” said author Charles Muirhead. “Because they occupy nearshore and shelf waters of the Gulf Coast and western North Atlantic — areas with intense human activity — they are frequently exposed to overlapping stressors throughout much of their life cycle.”

Like many sea creatures, Kemp’s ridleys are sensitive to sound. Sound waves, especially low frequency waves produced by ships and other machinery, travel long distances underwater, and they tend to overlap with the sounds these animals rely on for navigating their environment.

To evaluate their hearing range, the researchers placed noninvasive sensors on the turtles’ heads and measured the electrical signals transmitted along their auditory nerves. They played sounds ranging from 50 hertz — close to the low end of human hearing — all the way up to 1,600 hertz. They found that the turtles could hear best at around 300 hertz, and their hearing started to decline at higher frequencies.

“Our findings indicate that the turtles are most sensitive in the same low-frequency band where much industrial and vessel noise occurs,” said Muirhead. “This does not automatically mean that harmful effects are occurring, but it highlights where further monitoring and targeted impact studies should be focused.”

Next, the researchers plan on studying how sea turtles respond to sounds in real environmental conditions, as well as understanding the relationship between the measured sound signals and the physical effects of noise on turtles.

“These efforts will help refine our understanding of how human-caused noise interacts with sea turtle sensory systems. They will also support evidence-based management approaches aimed at minimizing unintended impacts while balancing human activities in coastal and offshore waters,” said Muirhead.

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The article “Underwater hearing sensitivity of the Kemp’s ridley sea turtle (Lepidochelys kempii)” is authored by Charles A. Muirhead, Wendy E.D. Piniak, Douglas P. Nowacek, and Craig A. Harms. It will appear in The Journal of the Acoustical Society of America on Feb. 3, 2026 (DOI: 10.1121/10.0041867). After that date, it can be accessed at https://doi.org/10.1121/10.0041867.

ABOUT THE JOURNAL

The Journal of the Acoustical Society of America (JASA) is published on behalf of the Acoustical Society of America. Since 1929, the journal has been the leading source of theoretical and experimental research results in the broad interdisciplinary subject of sound. JASA serves physical scientists, life scientists, engineers, psychologists, physiologists, architects, musicians, and speech communication specialists. See https://pubs.aip.org/asa/jasa.

ABOUT THE ACOUSTICAL SOCIETY OF AMERICA

The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.

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Journal

The Journal of the Acoustical Society of America

DOI

10.1121/10.0041867 

Article Title

Underwater hearing sensitivity of the Kemp’s ridley sea turtle (Lepidochelys kempii)

Article Publication Date

3-Feb-2026

 

Accurately predicting Arctic sea ice in real time

Sea ice coverage is difficult to predict short-term, but sea ice health is crucial for the global climate.

American Institute of Physics

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Regional subdivisions (left) and seasonal decline of total Arctic sea ice extent during summer melt (right), highlighting 2024, 2023, and the record low of 2012.

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Credit: Kondrashov et al.

WASHINGTON, Feb. 3, 2026 — Arctic sea ice has large effects on the global climate. By cooling the planet, Arctic ice impacts ocean circulation, atmospheric patterns, and extreme weather conditions, even outside the Arctic region. However, climate change has led to its rapid decline, and being able to make real-time predictions of sea ice extent (SIE) — the area of water with a minimum concentration of sea ice — has become crucial for monitoring sea ice health.

In Chaos, by AIP Publishing, researchers from the United States and the United Kingdom reported accurate, real-time predictions of SIE in Arctic regions. Sea ice coverage is at its minimum in September, making the month a critical indicator of sea ice health and the primary target of the work.

“Indigenous Arctic communities depend on the hunting of species like polar bears, seals, and walruses, for which sea ice provides essential habitat,” said author Dimitri Kondrashov. “There are other economic activities, such as gas and oil drilling, fishing, and tourism, where advance knowledge of accurate ice conditions reduces risks and costs.”

The researchers’ approach treats sea ice evolution as a set of atmospheric and oceanic factors that oscillate at different rates — for example, climate memory at long timescales, annual seasonal cycles, and quickly changing weather — while still interacting with one another. They used the National Snow and Ice Data Center’s average daily SIE measurements from 1978 onward to find the relationships between these factors that affect sea ice.

Testing their prediction method live in September 2024, and retroactively for Septembers of past years, the group confirmed their technique is generally accurate and can capture effects from subseasonal to seasonal timescales. They predicted SIE ranging from one to four months out and found their predictions outperformed other models.

In general, long-term climate forecasts tend to be easier and more reliable than short-term predictions. However, by incorporating regional data into their model, the researchers were able to improve short-term ice and weather estimates.

“The model includes several large Arctic regions composing [the] pan-Arctic,” said Kondrashov. “Despite large differences in sea ice conditions from year to year in different regions, the model can pick it up reasonably accurately.”

The group plans to improve their model by including additional oceanic and atmospheric variables, such as air temperature and sea level pressure. These variables can cause fast changes and short-term fluctuations that are not currently reflected in the model, and the researchers hope these additions will further enhance the predictability of summertime Arctic sea ice.

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The article “Accurate and robust real-time prediction of September Arctic sea ice” is authored by Dimitri Kondrashov, Ivan Sudakow, Valerie N. Livina, and QingPing Yang. It will appear in Chaos on Feb. 3, 2026 (DOI: 10.1063/5.0295634). After that date, it can be accessed at https://doi.org/10.1063/5.0295634.

ABOUT THE JOURNAL

Chaos is devoted to increasing the understanding of nonlinear phenomena in all areas of science and engineering and describing their manifestations in a manner comprehensible to researchers from a broad spectrum of disciplines. See https://pubs.aip.org/aip/cha.

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The researchers’ approach for modeling sea ice extent transforms complex Arctic data (left) into simpler rhythmic patterns (center), which are then modeled as coupled oscillators (right) to generate accurate forecasts, mimicking how different natural cycles interact.

Credit

Kondrashov et al.

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Journal

Chaos An Interdisciplinary Journal of Nonlinear Science

DOI

10.1063/5.0295634 

Article Title

Accurate and robust real-time prediction of September Arctic sea ice

Article Publication Date

3-Feb-2026