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First-of-its-kind measurement may help physicists learn about gluons, which hold together nuclei in atoms

A team of physicists has embarked on a journey where few others have gone: into the glue that binds atomic nuclei. The resultant measurement, which was extracted from experimental data taken at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility, is the first of its kind and will help physicists image particles called gluons.

The paper revealing the results is published and featured as an editor’s suggestion in Physical Review Letters.

Gluons mediate the strong force that “glues” together quarks, another type of subatomic particle, to form the protons and neutrons situated at the center of atoms of ordinary matter. While previous measurements have allowed researchers to learn about the distribution of gluons in solitary protons or neutrons, they know less about how gluons behave inside protons or neutrons bound in nuclei.

“This result represents a big step forward in learning about where that gluon field is located in a proton,” said Axel Schmidt, an assistant professor of physics at George Washington University and a principal investigator of this work. “We see evidence that it might be changing when a proton or neutron is inside a nucleus.”

A charming guidepost particle

For more than four decades, the physics community has known that quarks, the building blocks of our visible universe, move slower when they make up a proton or neutron that’s inside an atomic nucleus compared to a solitary proton or neutron. But physicists haven’t been able to figure out why this phenomenon, known as the EMC effect, occurs.

To learn more about it, and the strong force in general, physicists need to probe gluons the way they probed quarks. However, measuring the distribution of gluons, which are neutral, is more challenging than measuring the distribution of electrically charged quarks.

“Studying these neutral particles that only interact by the strong force is much more difficult,” said Lucas Ehinger, a graduate student at the Massachusetts Institute of Technology who worked on the analysis that led to this measurement. “We know a whole lot less about them and their dynamics in nuclei, including whether there’s any kind of potential EMC effect with them.”

This work takes a step toward changing this. And it does so by measuring a different particle altogether: J/ψ (or J/psi).

The experiment was carried out at Jefferson Lab’s Continuous Electron Beam Accelerator Facility, a DOE user facility that supports the research of more than 1,650 nuclear physicists worldwide. CEBAF’s electron beams can be used to also produce beams of high-energy photons for experiments that explore atomic nuclei.

Shooting a beam of photons at protons and neutrons can produce J/ψ particles, which each promptly decays into an electron and positron. Detecting this pair shows how many J/ψ were produced during an experiment. J/ψ is made of charm quarks. Because charm quarks, one of the six flavors of quarks, are not part of the proton or neutron, physicists know J/ψ is born from the interaction between the photon and gluon, which can produce particles containing any flavor of quark.

The production of J/ψ is a well-known tool for studying gluon distributions. Previous experiments at Jefferson Lab used a photon beam to measure J/ψ production of a solitary proton in the GlueX detector. To produce J/ψ, which is a heavy particle, the energy of the photon beam had to be very high—at least 8.2 GeV.

In this work, the experimental team also used a photon beam to produce J/ψ. However, they were able to do so using photons below the 8.2 GeV energy threshold and measure the results in the GlueX detector.

This was possible because they were using different nuclei as targets: deuterium, helium and carbon. Unlike a solitary proton or neutron target, the protons and neutrons inside these nuclei are moving around. Their kinetic energy combines with the energy of the incoming below-threshold photon, and, together, they offer enough energy to create J/ψ.

As a result, the team was the first to measure J/ψ photoproduction below the photon energy threshold required for a stationary proton. Because this measurement was taken off nuclei, it images the glue holding together protons and neutrons bound inside the nucleus.

“We are in this frontier of nuclear glue. Essentially, nothing is known, so everything you measure is informative,” said Or Hen, professor of physics at MIT and a principal investigator of this work. “It’s super exciting and super difficult at the same time.”

Charting a map for future measurements

One reason this pathfinder measurement was difficult is because there weren’t previous measurements to guide it. Embarking on the analysis, the team wasn’t even sure it was possible. The experiment that collected this data wasn’t originally supposed to measure subthreshold J/ψ production; it was more of a hopeful add-on.

Thankfully, the researchers had Jackson Pybus on their team. Pybus led the bulk of the analysis while he was a graduate student at MIT. He called upon his training during a summer abroad in Germany. There, he had worked with a theoretician to learn about light-front dynamics.

This approach generally applies to quantum field theories, which describe relativistic particle behavior (particles moving close to the speed of light). In this research, it is most useful in describing particle systems like nuclei. Applying tricks from this theoretical method allowed Pybus and the team to extract this measurement.

“This work is both unique in terms of what physics it teaches us, but also in terms of the techniques that a graduate student implemented to get at that physics,” Hen said. “None of us, except for Jackson, would have been able to do this work. He deserves a lot of credit.”

When the experimentalists compared their sub-threshold measurement to theoretical predictions, they saw that more J/ψ were produced than theory predicted. This disparity hints that the nuclear glue behaves differently than the glue in solitary protons or neutrons, but more data are needed to determine exactly how. Fortunately, these results will serve as a map to guide similar future measurements.

“Now that we know that we can do this measurement, we would really like to optimize a longer experiment to measure this in detail and quantitatively pin down some of these potentially exotic effects, where we really only have a first look right now,” said Pybus, who is now a postdoctoral fellow at Los Alamos National Laboratory.

The data used in this work—made up of only dozens of J/ψ measurements– were collected during a relatively short six-week run in 2021. The team is proposing an experiment dedicated to studying the nuclear glue, again using CEBAF’s photon beam with the GlueX apparatus.

“Imagine what we could do if we had 100 days of dedicated accelerator time to really study this reaction,” Hen said. “We are now doing the very hard work of mapping out the frontier of the strong nuclear force with the hope that one day—maybe not in our lifetime—humanity’s improved knowledge will enable better technology and more sustainable power sources.”

These results could also steer gluon experiments at the forthcoming Electron-Ion Collider (EIC), which plans to further investigate gluons.

“We would like to learn about this problem and have a good handle of what’s going on and where to look prior to this machine turning on,” Schmidt said.

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Friction variation creates Tête de Moine’s signature cheese flowers

Tête de Moine, a semi-hard Swiss cheese that often finds its way onto charcuterie boards and salads, not only brings a rich, nutty and creamy flavor, but also adds a dramatic flare to the presentation. Instead of slicing, this cheese is shaved into delicate rosettes using a tool called a Girolle whose rotating blade gently scrapes thin layers of cheese into ruffled curls. These pretty cheese flowers are known to enhance the flavor and texture due to their high surface-to-volume ratio.

The unusual way Tête de Moine forms wrinkles when shaved, piqued the interest of a team of physicists who, in a study published in Physical Review Letters, set out to investigate the physical mechanisms behind these intricate shapes.

Similar morphogenetic patterns can be observed in the frilly edges of leaves, fungi, corals, or even torn plastic sheets, but the mechanisms that explain the similar shapes in these materials fail to account for the distinctive physical properties of cheese.

This study discovered that the frilly shapes arise as a result of variations in the cheese’s properties—such as firmness and elasticity—within a single Tête de Moine wheel, from the center to the edge. The distinctive flower shape is driven mainly by changes in friction caused by the cheese’s inhomogeneous texture and not by variations in mechanical properties like yield stress or fracture energy.

A typical Girolle has a wooden base, a central steel spike, and a removable rotating blade with a handle attached to it. Before serving, the cheese is skewered onto a steel rod until it reaches the wooden base, and then the rotating blade that sits on the cheese is mounted onto the rod. Rotating the blade’s handle scrapes off thin layers of the frilly cheese.

Schematic illustration of the experimental setup. Inset: depth of cut h0 as a function of vertical load per unit length of the blade Ft. Credit: Phys. Rev. Lett. (2025). DOI: https://doi.org/10.1103/PhysRevLett.134.208201
For this study, the researchers opted for cheese wheels from a single brand and age was used to maintain consistency. They also modified the Girolle to include: a motorized base of the Girolle to rotate the cheese at a steady speed of 1.14 rad/s, the blade at a fixed height and a tilt of −14.7° to ensure consistent slicing and adjustable weights to control the vertical cutting force precisely.

To understand the physical forces behind the cheese’s unique shape, the team measured key properties like depth of cut, mechanical properties such as Young’s modulus, yield stress, and fracture energy, as well as the friction coefficient at various positions on the cheese wheel.

They also integrated steady, real-time imaging into the setup, capturing side-view snapshots of the cutting process. This allowed them to visually confirm the cutting mechanism and observe how the cheese curls formed along the wheel’s edge.

a) Side view of instantaneous snapshots of the cheese layer formation on different radial positions x from the edge periphery, for Ft = 0.2 N/mm. b) Sketch illustrating the shear strain in a 2D plastic flow during cutting. Credit: Phys. Rev. Lett. (2025). DOI: https://doi.org/10.1103/PhysRevLett.134.208201
The experiments revealed that the cheese flowers form due to inhomogeneous plastic contraction during scraping, not from elastic deformation.

As the cheese wheel ages, it matures at different rates in different areas—the core remains softer while the edge becomes harder. This results in varying friction across the wheel, with much greater contraction in the inner core region of the cheese flower, leading to its characteristic buckling and frilly shape.

This was further confirmed by the observation that removing the low-friction outer layer produced flat and non-frilly cheese slices.

The researchers highlight that the shaping mechanism presented in this study could help develop new tools for the controlled processing of soft materials and enable the design of complex forms through a simple scraping technique.

by Sanjukta Mondal

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Team describes how to produce ‘green’ steel from toxic red mud

by Max Planck Society

Team describes how to produce 'green' steel from toxic red mud
Phase evolution of red mud with hydrogen plasma processing and mechanism of iron recovery. Credit: Nature (2024). DOI: 10.1038/s41586-023-06901-z

The production of aluminum generates around 180 million tons of toxic red mud every year. Scientists at the Max-Planck-Institut für Eisenforschung, a center for iron research, have now shown how green steel can be produced from aluminum production waste in a relatively simple way. In an electric arc furnace similar to those used in the steel industry for decades, they convert the iron oxide contained in the red mud into iron using hydrogen plasma.

With this process, almost 700 million tons of CO2-free steel could be produced from the 4 billion tons of red mud that have accumulated worldwide to date—which corresponds to a good third of annual steel production worldwide. As the Max Planck team shows, the process would also be economically viable.

According to forecasts, demand for steel and aluminum will increase by up to 60% by 2050. Yet the conventional production of these metals has a considerable impact on the environment. Eight percent of global CO2 emissions come from the steel industry, making it the sector with the highest greenhouse gas emissions. Meanwhile, aluminum industry produces around 180 million tons of red mud every year, which is highly alkaline and contains traces of heavy metals such as chromium.

In Australia, Brazil and China, among others, this waste is at best dried and disposed of in gigantic landfill sites, resulting in high processing costs. When it rains heavily, the red mud is often washed out of the landfill, and when it dries, the wind can blow it into the environment as dust.

In addition, the highly alkaline red mud corrodes the concrete walls of the landfills, resulting in red mud leaks that have already triggered environmental disasters on several occasions, for example in China in 2012 and in Hungary in 2010. In addition, large quantities of red mud are also simply disposed of in nature.

Potential to save 1.5 billion tons of CO2 in the steel industry

“Our process could simultaneously solve the waste problem of aluminum production and improve the steel industry’s carbon footprint,” says Matic Jovičevič-Klug, who played a key role in the work as a scientist at the Max-Planck-Institut für Eisenforschung. In a study published in the journal Nature, the team shows how red mud can be utilized as a raw material in the steel industry. This is because the waste from aluminum production consists of up to 60% iron oxide.

The Max Planck scientists melt the red mud in an electric arc furnace and simultaneously reduce the contained iron oxide to iron using a plasma that contains 10% hydrogen. The transformation, known in technical jargon as plasma reduction, takes just ten minutes, during which the liquid iron separates from the liquid oxides and can then be extracted easily. The iron is so pure that it can be processed directly into steel.

Green steel from toxic red mud
The generation, storage and hazards of red muds and solution with hydrogen plasma treatment. Credit: Nature (2024). DOI: 10.1038/s41586-023-06901-z

The remaining metal oxides are no longer corrosive and solidify on cooling to form a glass-like material that can be used as a filling material in the construction industry, for example. Other research groups have produced iron from red mud using a similar approach with coke, but this produces highly contaminated iron and large quantities of CO2. Using green hydrogen as a reducing agent avoids these greenhouse gas emissions.

“If green hydrogen would be used to produce iron from the 4 billion tons of red mud that have been generated in global aluminum production to date, the steel industry could save almost 1.5 billion tons of CO2,” says Isnaldi Souza Filho, Research Group Leader at the Max-Planck-Institut für Eisenforschung.

An economical process, including with green hydrogen and electricity

The heavy metals in the red mud can also be virtually neutralized using the process. “After reduction, we detected chromium in the iron,” says Jovičevič-Klug. “Other heavy and precious metals are also likely to go into the iron or into a separate area. That’s something we’ll investigate in further studies. Valuable metals could then be separated and reused.”

Additionally, heavy metals that remain in the metal oxides are firmly bound within them and can no longer be washed out with water, as can happen with red mud.

However, producing iron from red mud directly using hydrogen not only benefits the environment twice over; it pays off economically too, as the research team demonstrated in a cost analysis. With hydrogen and an electricity mix for the electric arc furnace from only partially renewable sources, the process is worthwhile, if the red mud contains 50% iron oxide or more.

If the costs for the disposal of the red mud are also considered, only 35% iron oxide is sufficient to make the process economical. With green hydrogen and electricity, at today’s costs—also taking into account the cost of landfilling the red mud—a proportion of 30 to 40% iron oxide is required for the resulting iron to be competitive on the market.

“These are conservative estimates because the costs for the disposal of the red mud are probably calculated rather low,” says Isnaldi Souza Filho. And there’s another advantage from a practical point of view: electric arc furnaces are widely used in the metal industry—including in aluminum smelters—as they are used to melt down scrap metal. In many cases, the industry would therefore need to invest only a little to become more sustainable.

“It was important for us to also consider economic aspects in our study,” says Dierk Raabe, Director at the Max-Planck-Institut für Eisenforschung. “Now it’s up to the industry to decide whether it will utilize the plasma reduction of red mud to iron.”

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Record-breaking performance in data security achieved with quantum mechanics

A joint team of researchers led by scientists at King Abdullah University of Science and Technology (KAUST) and King Abdulaziz City for Science and Technology (KACST) has reported the fastest quantum random number generator (QRNG) to date based on international benchmarks. The QRNG, which passed the required randomness tests of the National Institute of Standards and Technology, could produce random numbers at a rate nearly a thousand times faster than other QRNG.

“This is a significant leap for any industry that depends on strong data security,” said KAUST Professor Boon Ooi, who led the study, which is published in Optics Express. KAUST Professor Osman Bakr also contributed to the study.

Random number generators are critical for industries that depend on security, such as health, finance, and defense. But the random number generators currently used are vulnerable because of an intrinsic flaw in their design.

“Most random number generators are ‘pseudorandom number generators.’ In other words, they seem random, but in reality, they are complicated algorithms that can be solved. QRNGs do not suffer from this concern,” explained Ooi.

The reason is that QRNG uses the principles of quantum mechanics to produce a truly unpredictable random number. The high random number generation rate reported in the new study was the result of innovations made by the scientists in the fabrication and the post-processing algorithms of the device.

The QRNG was constructed using micro-LEDs (light emitting diodes) less than a few micrometers in size, which reduces their energy demands and suggests the QRNG is portable, expanding the types of applications. In addition, the National Institute of Standards and Technology is recognized internationally for providing benchmarks to ascertain the quality of randomness.

Dr. Abdullah Almogbel, a contributor of the study who is also a researcher at the Microelectronics and Semiconductors Institute and director of the Center of Excellence for Solid-State Lighting at KACST, stated, “KACST, in its capacity as the national laboratory, is committed to advancing applied research that directly supports the objectives of Saudi Arabia’s Vision 2030—particularly in establishing global leadership across strategic sectors, including quantum-enabled innovations.

“Undertaking such research initiatives is expected to generate substantial value for a wide range of industries and further solidify their global standing.”

by King Abdullah University of Science and Technology

edited by Gaby Clark, reviewed by Robert Egan

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Strategies for enhancing the performance of nickel single-atom catalysts for the electroreduction of CO₂ to CO

by Ziyan Yang

Strategies for enhancing the performance of nickel single-atom catalysts for the electroreduction of CO2 to CO
Strategies to enhance the performance of nickel single-atom catalysts for the electroreduction of CO2 to CO. Credit: Yuhang Li, Chunzhong Li, East China University of Science and Technology, China

Electrocatalytic reduction of carbon dioxide (CO2) is considered as an effective strategy for mitigating the energy crisis and the greenhouse effect. Among the multiple reduction products, CO is regarded as having the highest market value as it is a crucial feedstock for Fischer-Tropsch process which can synthesize high-value long-chain hydrocarbons.

Since the carbon dioxide reduction reaction (CO2RR) has complex intermediates and multiple proton-coupled electron transfer processes, improving the reaction activity and products selectivity remain two great challenges.

Single-atom catalysts (SACs) have the advantages of high atom utilization, tunable coordination structure and excellent catalytic performance. In addition, due to the special electronic structure of nickel metal, it is more likely to lose electrons to form empty outermost d-orbitals and exhibit high activity and selectivity for CO2RR to generate CO.

A team of scientists have summarized the considerable progress of Ni SACs in recent years. Their work is published in Industrial Chemistry & Materials.

“Designing novel catalysts to improve the activity and selectivity of CO2RR is crucial for conquering the problem of energy crisis and environmental pollution,” said Yuhang Li, a Professor at East China University of Science and Technology, China,

“In this mini-review, we introduced three strategies used to improve the catalytic performance of Ni SACs, including different structures of supports, coordination structure regulation, and surface modification. In the end, we also summarized the existing challenges of Ni SACs and provided an outlook on future development in this field.”

SACs downsize the active sites to atomic scale and therefore get extraordinary electronic structure, powerful metal-support interactions, low-coordinated metal atoms, and maximum atom utilization at the same time. Hence, the application of SACs in CO2RR could effectively control the distribution of products and alleviate the cost of products separation.

“Some research based on crystal-field theory has indicated that the d-orbital electronic configurations of central metals are significant to the selectivity and activity of CO2RR,” Li said.

“In the case of nickel as the central metal atom, it is more likely to form the vacant outermost d-orbital to facilitate the electron transfer between the C atom of CO2 and the Ni atom. Therefore, the absorbed CO2 molecules can be efficiently activated. Ni SACs can also minimize the reaction potential of CO2-CO conversion, which is of great importance to enhance the selectivity towards CO.”

“Ni SACs have achieved continuous progress in recent years. From a microscopic point of view, the design strategies include choosing different substrates, regulating the coordination structure and modifying the catalyst surface. The electronic structure of the active center is the most crucial factor affecting catalytic performance,” Li said.

There is still tremendous potential for Ni SACs in future designs and applications. Precise modulation of the microstructure provides more active sites and therefore further enhances the performance of Ni SACs. Optimization of the electrolytic cells and development of more types of electrolytes can expand the range of Ni SACs applications and enable large-scale commercialization in the future.

In addition, researchers think that developing more in-situ techniques to gain deeper insights into the relationship between material structure and properties can provide valuable guidance for designing higher-value Ni SACs.

“In this mini-review, our main goal is to provide readers with the current research progress in Ni SACs in CO2RR and to show our insights into the design and application of single-atom catalysts,” Li said.

The research team includes Ziyan Yang, Rongzhen Chen, Ling Zhang, Yuhang Li, and Chunzhong Li from East China University of Science and Technology.

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A new method to control the rovibrational ground state of a single molecular hydrogen ion

 The precise measurement of states in atomic and molecular systems can help to validate fundamental physics theories and their predictions. Among the various platforms that can help to validate theoretical predictions are so-called diatomic molecular hydrogen ions (MHI), molecular ions that consist of two hydrogen nuclei (i.e., protons or their isotopes) and a single electron.

Compared to atomic ions, these molecular ions have a more complex internal structure, as they contain two nuclei instead of one. Even when they are in their lowest possible electronic energy level (i.e., the electron’s ground state), these two nuclei can still rotate and vibrate, producing a wide range of rovibrational states.

Researchers at the Max Planck Institute for Nuclear Physics recently introduced a new method to precisely control and non-destructively measure the rovibrational ground state of a single molecular hydrogen ion in a Penning trap (i.e., a device that confines charged particles using static electric and magnetic fields).

This method, outlined in a paper published in Physical Review Letters, could open new possibilities for the manipulation and measurement of rich quantum states in individual molecular ions.

“The work for the paper was inspired by the goal of the fundamental physics research community to compare H2+ and its antimatter counterpart H2- in the future,” Charlotte König, first author of the paper, told Phys.org. “An overview on this topic and measurement proposals can be found in a paper by Myers published in 2018.

Therefore, we have now developed and demonstrated nondestructive state detection and measurement techniques on a single molecular hydrogen ion (HD+) in a Penning trap; applicable to other molecular ions with an unpaired electron spin, i.e. to H2+ and H2-.”

The new method developed by König and her colleagues relies on an effect known as the continuous Stern Gerlach effect, first unveiled in the 1980s. This is a physical phenomenon that can be leveraged to measure the orientation of the magnetic moment (e.g., the electron spin) of single trapped particles, including ions, without destroying them.

“In our experiments, the orientation of the electron spin in the external magnetic field (B) of the Penning trap is mapped onto the ion motion in a magnetic bottle (B=B0+B2 x2), which is an established technique for atomic ions in Penning traps,” explained König.

“In the molecule, the energy splitting between electron spin up or down is unique to each rovibrational and hyperfine state. Therefore, resonantly driving an electron spin transition (detected by the continuous Stern Gerlach effect), gives us the information about which internal quantum state the ion is in.”

Using their newly proposed method, König and her colleagues demonstrated the confinement of an externally produced molecular hydrogen ion (HD+) for more than a month. In addition, they were able to detect the internal quantum state of this ion and control its hyperfine state.

“These are necessary requirements to enable future measurements of the antimatter molecular hydrogen ion H2- for tests of the fundamental charge-parity-time reversal symmetry,” said König. “The techniques could also be applied to other molecular ions, for which single particle control is envisioned.”

The recent research by this team of researchers and the new techniques it introduced could be used in future studies probing the states of both matter and antimatter molecular systems. Ultimately, it could help to unveil deviations from the Standard Model, shedding light on the limitations of current physical predictions.

“Our future research plans will include applying the demonstrated techniques to high-precision spectroscopy of single molecular hydrogen ions in our Penning trap apparatus,” added König. “This research will address either the hyperfine and Zeeman structure or the rovibrational level structure.”

by Ingrid Fadelli

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Solving an age-old mystery about crystal formation

by Laurie Fickman, University of Houston

Solving an age-old mystery about crystal formation
Peter Vekilov, University of Houston Frank Worley Professor of Chemical and Biomolecular Engineering, has published that incorporation of molecules into crystals occurs in two steps, divided by an intermediate state. Credit: University of Houston

A million years ago, the oldest known species to walk upright like a human, the Homo erectus, had a human-like fascination with crystals. Historians can even pin down the possible reasons—crystals didn’t look like anything around at the time—trees, valleys, mountains. Crystals were a material to ponder, a fascinating diversion for the mind.

To this day, the human preoccupation with the magic of crystals continues to fill the mind’s eye of scientists who have developed ways to use crystals for everything from malaria cures to solar cells and semiconductors, catalysts and optical elements. Over the years crystals have become crucial constituents of the technologies that enable modern civilization.

University of Houston researcher Peter Vekilov and Frank Worley Professor of Chemical and Biomolecular Engineering, have published in PNAS an answer to how crystals are formed and how molecules become a part of them.

“For decades crystal growth researchers have dreamt of elucidating the chemical reaction between incoming molecules and the unique sites on a crystal surface that accept them, the kinks,” said Vekilov. “The mechanism of that reaction, i.e., the characteristic time scale and length scale, possible intermediates and their stabilities, has remained elusive and subject to speculation for over 60 years.”

The main obstacle to deeper understanding has been the lack of data on how molecules join in, connected to the complicated process of moving from the solution to where they grow.

To unravel the chemical reaction between a molecule that dissolves in liquid (solute) and a kink, Vekilov mobilized two transformational strategies, one using full organic pairs and the second, using four solvents with distinct structures and functions. Working with the molecules, he combined state-of-the-art experimental techniques including time-resolved in situ atomic-force microscopy at near-molecular resolution, X-ray diffraction, absorption spectroscopy and scanning electron microcopy.

That’s when Vekilov made a revolutionary discovery: Incorporation into kinks may occur in two steps divided by an intermediate state and the stability of this middle state is key in how crystals grow. It basically decides how fast or slow the crystals form because it affects how easily things can join in during the process

Though the new discoveries don’t date back to Homo sapien times, they do solve a 40-year-old riddle for Vekilov.

“The notions of an intermediate state and its decisive role in crystal growth refute and replace the dominant idea in the field, brought up by A.A. Chernov, my Ph.D. advisor, that the activation barrier for growth is determined by the solute-solvent interactions in the solution bulk,” he said.

The new paradigm of two step incorporation, mediated by an intermediate state, could help in understanding how small parts in a liquid can influence the detailed shapes of crystals found in nature.

“Equally important, this paradigm will guide the search for solvents and additives that stabilize the intermediate state to slow down the growth of, for instance, undesired polymorphs,” Vekilov said.

Vekilov’s team includes Jeremy Palmer, Ernest J and Barbara M Henley Associate Professor of chemical and biomolecular engineering; former graduate students Rajshree Chakrabarti and Lakshmanji Verma; and Viktor G. Hadjiev, Texas Center for Superconductivity at UH.

More information: Rajshree Chakrabarti et al, The elementary reactions for incorporation into crystals, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2320201121

Provided by University of Houston 

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New high-resolution laser device reads millimeter-scale text from a mile away

You are the protagonist in a thriller. One morning, an unknown caller with a distorted voice says, “To save your city, solve the puzzle. Go to the coordinates. X marks the clue.” You rush to the spot and see an X on a distant billboard, too far to read. Your vision is sharp, but not that sharp. So, what do you do? A new laser emitter designed by a team of researchers from China could come to the rescue.

According to the study published in Physical Review Letters, the developed setup includes multiple laser emitters that enable super-resolution imaging of targets as small as millimeters in scale from a 1.36 kilometers (0.85 miles) distance in an outdoor urban environment. The device successfully images letter-shaped physical targets measuring 8×9 mm, with letter widths of 1.5 mm, placed at the far end of its imaging range.

Interferometry is a widely used imaging technique in astronomy which works by merging light from different sources to create an interference pattern. These interference patterns are formed when light waves interact to either reinforce or cancel each other depending on their phase differences. These patterns carry detailed information about the object or phenomenon being studied.

Intensity interferometry, on the other hand, does not rely on combining light amplitudes or maintaining phase information but on light from a single source being measured separately by two detectors or telescopes, and the variations in their recorded intensities are compared.

Studying intensity fluctuations, correlations and their changes with the distance between the detectors can help extract spatial details about the object being studied.

New high-resolution laser device reads milimeter-scale text from a mile away
Experimental schematic. The active optical intensity interferometer consists of two parts: the source plane and the detection plane. Credit: Phys. Rev. Lett. (2025). DOI: 10.1103/PhysRevLett.134.180201

What makes intensity interferometry stand out? It can cut through atmospheric turbulence and ignore flaws in telescope optics—making it ideal for long-distance, high-resolution imaging. Yet, its applications have mostly been limited to observing bright stars or objects that can be lit up with nearby light sources.

Scientists have attempted to expand its scope to active imaging applications such as light detection and ranging or LiDAR, but the lack of suitable thermal light sources and robust image reconstruction algorithms make the process challenging.

To overcome these issues, the researchers created an intensity interferometer setup with pseudothermal illumination achieved by superimposing light from 8-phase-independent multiple laser emitters. This setup included two telescopes and an infrared laser system on a shared optical bench.

The laser system produced thermal illumination, and reconstructed sparse, noisy data being collected into a high-resolution image with the help of a computational algorithm.

To test the super-resolution capabilities of the device, the letters “USTC” were crafted out of hollowed-out blackened aluminum sheets which were then covered in retroreflective sheets and used as a complex imaging target positioned over a kilometer away.

New high-resolution laser device reads milimeter-scale text from a mile away
Data processing. Credit: Phys. Rev. Lett. (2025). DOI: 10.1103/PhysRevLett.134.180201

Using the designed active intensity interferometer, the researchers successfully demonstrated super-resolution imaging of millimeter-scale targets at a distance of 1.36 km in an outdoor urban environment. The imaging system achieved a resolution of 3 mm, which is 14 times higher than the diffraction limit of a single telescope, typically around 42.5 mm.

Once scaled for use beyond the laboratory, this device could significantly accelerate advancements in long-range, high-resolution remote sensing, surveillance, and non-invasive imaging in challenging environments.

More information: Lu-Chuan Liu et al, Active Optical Intensity Interferometry, Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.180201

Journal information: Physical Review Letters 

by Sadie Harley, reviewed by Robert Egan

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Eco-friendly rare earth element separation: A bioinspired solution to an industry challenge

From smartphones to wind turbines, rare earth elements (REEs) are an essential part of the hardware in many advanced technologies. These elements, which include the lanthanides along with scandium and yttrium, are the backbone of industries that rely on unique properties such as luminescence, magnetism and catalytic ability. In fact, as our world moves toward more sustainable energy solutions and increasingly sophisticated technologies, the demand for REEs is projected to grow substantially.

There’s one catch, however: REEs are difficult to extract and even harder to separate. These elements, despite their name, aren’t actually rare in terms of abundance. What makes them “rare” is their dispersion throughout the Earth’s crust and their chemical similarities, which make them incredibly challenging to isolate from one another.

Current separation methods—largely reliant on toxic solvents like kerosene—are not only inefficient, but also harmful to people and the environment. Additionally, while the U.S. once dominated REE mining and production, environmental restrictions on current separation methods have limited domestic production.

Kathleen Stebe, Richer & Elizabeth Goodwin Professor in Chemical and Biomolecular Engineering (CBE), is tackling this challenge head-on with a collaborative group of researchers across five institutions under the support of a grant from the Department of Energy. Stebe is leading a groundbreaking research initiative that aims to create an eco-friendly, bioinspired process for separating REEs that would also avoid shipping semi-processed REEs to other countries for purification.

“Current separation methods use kerosene and extractants-molecules that bind the REE cations, a positively charged particle, that create issues, both environmentally and in terms of efficiency,” says Stebe. “The separation process is not selective enough to efficiently separate lanthanides, meaning that it has to be repeated many times to achieve REEs in sufficient purity. The whole method is cumbersome and creates unnecessary waste.”

Stebe, along with a team of researchers from Penn, the City College of New York, the University of Illinois Chicago, Northwestern University and the University of Chicago, look to human biology to find the molecule best suited for the job of separation: peptides.

Bioinspired interfaces: Drawing on nature’s expertise

In nature, organisms have evolved proteins that selectively bind to specific ions, despite their similar properties. A perfect example of this is calcium-binding proteins in the human body, which can distinguish between calcium and magnesium ions, even though both have the same charge.

“We are applying this concept to create a similar level of selectivity for rare earth elements,” says collaborator E. James Petersson, professor of chemistry, biochemistry and biophysics at Penn’s School of Arts & Sciences. “By using peptide-based molecules—specifically, a truncated version of the EF-hand motif, which is naturally found in calcium-binding proteins—we are designing molecules that can selectively bind to specific rare earth elements.”

This EF-hand motif refers to the structure and mechanism through which these naturally occurring proteins and peptides are able to differentiate between two very similar molecules.

“The structure resembles a hand,” says Stebe, “and each ‘finger’ of the hand is laden with a carboxyl or carbonyl group that binds to cations floating around in solution. It’s a beautiful and complex structure that can recognize the nuanced and subtle differences between two nearly indistinct cations, and then capture and hold onto whichever cation it is ‘looking’ for. This is extremely important for separating REEs, which differ in size by only one-tenth of an angstrom.”

In the team’s recent study published in the Proceedings of the National Academy of Sciences, they found that EF-hand-containing peptides could bind to the peptide-cation complex and capture it at the aqueous-air interface. The vision includes using bubbles to separate specific lanthanides from a mixture. Once bound to the peptides in an aqueous solution, the REEs will rise to the surface, where they are trapped in a foam at the water-air interface, a separation technique called ion foam flotation.

“My primary area of research is in interfacial science, studying the adsorption of surface-active molecules—surfactants and soap molecules—to the air-water interface,” says co-author Charles Maldarelli, professor of chemical engineering at The City College of New York. “This study gave me the opportunity to apply my expertise to the adsorption of peptides and peptide-metal complexes at the interface.”

Felipe Jimenez-Angeles, research associate professor at Northwestern University, performed many of the molecular dynamics simulations in this study. “I am fascinated that these peptides can separate ions that only differ by a few tenths of an Angstrom in diameter via the differences in the electrostatic forces at the atomic scale. The water-soluble peptide reconfigures when it captures the ion and becomes insoluble in water, resulting in its adsorption to the air-water interface.”

The team’s next steps in this research will be investigating how to scale this process, allowing them to isolate target REEs and collect them at usable quantities in a way that is much more efficient and environmentally friendly.

The collaborative effort behind the innovation

What makes this project truly innovative is the collaboration across multiple universities and disciplines. Each institution brings unique expertise to the project, from synthetic chemistry to surface material properties, and even X-ray experiments.

“This is really the first time my lab has used biology to solve chemistry problems,” says Petersson. “Normally, we focus on creating chemical probes to study biology, often looking at neurodegenerative disorders like Parkinson’s disease. But the experience of working on this project has inspired me to explore other biological approaches to chemistry, including adapting disease-related proteins for applications in other fields like energy and sustainability.”

“I have long been interested in molecular interface interactions,” adds Ivan Dmochowski, Professor of Chemistry in Penn’s School of Arts & Sciences. “As an undergraduate, I made molecules that react with the surface of glass and gold, and studied the resulting monolayers that formed. Later I started looking at proteins at the air-water interface.”

Other key senior faculty involved in the research include Monica Olvera de la Cruz from Northwestern University, Raymond Tu from CCNY, Mark Schlossman from the University of Illinois at Chicago, and Daeyeon Lee, Ravi Radhakrishnan and Cesar de la Fuente at the University of Pennsylvania.

“It has been rewarding to both contribute to and learn from this effort,” continues Dmochowski. “To solve really challenging, societally relevant problems in 2025, we will need a wide range of technical expertise, and I am excited to continue working with this team of collaborators to do that.”

Looking ahead: The future of rare earth element recovery

As Stebe’s team continues their work, they are focused on fine-tuning the selectivity of the peptides and optimizing the process for bulk production. Their next steps include using specialized peptides designed by Petersson to enhance the fluorescence of the system, allowing for more precise tracking of the binding events. They also plan to use physics data to inform additional opportunities for improved specificity and look into developing new, synthetic molecules to make this method even more cost-effective and environmentally friendly.

“This is just the beginning,” says Stebe. “We have a lot of exciting new directions to explore, from using synthetic molecules instead of peptides to creating even more selective binding structures. The potential impact of this work goes far beyond just rare earth elements—it could revolutionize the way we approach material separation across many industries.”

More information: Luis E. Ortuno Macias et al, Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2411763121

Journal information: Proceedings of the National Academy of Sciences 

Provided by University of Pennsylvania 

by Melissa Pappas, University of Pennsylvania

Posted on

Advancing unidirectional heat flow: The next era of quantum thermal diodes

Heat management at the nanoscale has long been a cornerstone of advanced technological applications, ranging from high-performance electronics to quantum computing. Addressing this critical challenge, we have been deeply intrigued by the emerging field of thermotronics, which focuses on manipulating heat flux in ways analogous to how electronics control electric energy. Among its most promising advancements are quantum thermal diodes, which enable directional heat control, and quantum thermal transistors, which regulate heat flow with precision.

Thermal diodes, much like their electrical counterparts, provide unidirectional heat transfer, allowing heat to flow in one direction while blocking it in the reverse. We find this capability revolutionary for heat management, as it has the potential to transform numerous fields.

For instance, thermal diodes can significantly improve the cooling of high-performance electronics, where heat dissipation is a major bottleneck. They could also enable more efficient energy harvesting by converting waste heat into usable energy, contributing to sustainability efforts.

Additionally, they offer applications such as dynamically managing building temperatures, enhancing the performance of thermoelectric generators, or even improving spacecraft thermal systems, where precisely controlled heat flow is critical.

In our research, we have noticed that most quantum thermal device models to date have relied on simple quantum systems with two stable energy levels, such as qubits. However, we see significant potential to go beyond these limitations.

At the Advanced Computing and Simulation Laboratory (AχL), Monash University, Australia, we have been exploring higher-dimensional quantum systems that expand the capabilities of these devices. By integrating qubit-qutrit architectures, we have demonstrated directional heat flow with improved efficiency and scalability.

This breakthrough, published in APL Quantum, lays the groundwork for practical, high-performance thermotronic systems that could address challenges ranging from overheating in modern technology to advancing sustainable energy solutions. These advancements represent a critical step forward, promising to redefine heat management and energy efficiency in the quantum era.

Harnessing quantum asymmetry to regulate unidirectional heat flow

The quantum thermal diode, based on the interaction between a qutrit (a quantum system with three stable energy levels) and a qubit (a system with two stable energy levels), introduces a novel approach to unidirectional heat transfer.

This system leverages the inherent properties of quantum mechanics to create an asymmetric energy landscape that naturally favors heat flow in one direction, depending on the temperature gradient. This directional behavior is analogous to the way an electronic diode facilitates unidirectional current flow based on the potential difference across its terminals.

The key to this thermal diode lies in how the energy levels of the qubit and qutrit align and interact. By carefully configuring the combined energy levels, we can facilitate heat transfer along the desired temperature gradient while effectively blocking it in the opposite direction. This directional control is achieved through precise quantum interactions, which utilize specific shared energy levels between the qubit and qutrit to establish the necessary conditions for asymmetry in heat flow.

What makes this system particularly groundbreaking is its ability to operate as a nearly perfect thermal diode across a broad temperature range. Unlike classical thermal systems, the quantum nature of this device allows for precise tuning of its properties, including the spacing of energy levels and the coupling strengths between the qubit and qutrit. This tunability enables unprecedented control over the heat transfer process, making the device highly adaptable to various applications.

Whether improving the heat management of nanoscale devices or developing next-generation thermotronic systems, we believe this architecture represents a major step forward in thermal management technologies. By combining a qutrit and a qubit into a single system, this design not only achieves directional heat flow but also enhances efficiency, offering a practical and scalable solution for advanced thermotronics.

Shaping future technologies: The transformative potential of quantum thermal diodes

The development of a quantum thermal diode is a transformative breakthrough with significant implications for quantum thermodynamics and nanoscale engineering. By enabling precise control of heat flow at the quantum level, this innovation addresses challenges that traditional cooling methods cannot solve, particularly in quantum circuits and advanced nanoscale devices.

For example, quantum thermal diodes can regulate heat dissipation in quantum processors, ensuring stable and optimal performance where even slight overheating could lead to disruptions. Additionally, they open up new opportunities for energy harvesting by capturing waste heat generated in quantum systems and converting it into usable energy. This capability has the potential to drive sustainable energy solutions across numerous applications.

Beyond energy efficiency, we believe quantum thermal diodes could pave the way for thermal logic devices—thermal analogs to electronic diodes—allowing computation to be performed using heat flow rather than electric current. Such a development would represent an entirely new paradigm in computation, with applications in fields requiring unique architectures for energy and heat management.

Furthermore, these devices hold significant promise in specialized areas, such as biomedical technologies, where precise thermal regulation is critical for maintaining the performance of sensitive quantum sensors. They could also prove vital in space exploration, where managing the temperature of delicate quantum instruments in extreme environments is essential.

By improving the efficiency of heat dissipation and enabling directional control, quantum thermal diodes not only enhance the functionality of nanoscale devices but also set the stage for the next generation of technologies.

With the potential to develop quantum thermal transistors and other advanced thermotronic devices, we believe this innovation has the power to redefine how we approach thermal management and energy utilization in a quantum-driven world. From nanoscale engineering to space exploration, the transformative potential of quantum thermal diodes promises to shape the technologies of tomorrow.

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about Science X Dialog and how to participate.

More information: Anuradhi Rajapaksha et al, Enhanced thermal rectification in coupled qutrit–qubit quantum thermal diode, APL Quantum (2024). DOI: 10.1063/5.0237842

Bios:
Anuradhi Rajapaksha earned her B.Sc. in electrical and electronic engineering (with first-class honors) from University of Peradeniya, Sri Lanka in 2021. Currently she is a PhD candidate and a member of the Advanced Computing and Simulations Laboratory at the Department of Electrical and Computer Systems Engineering, Monash University, Australia under the supervision of Prof. Malin Premaratne.

Sarath D. Gunapala received a Ph.D. degree in physics from the University of Pittsburgh, Pittsburgh, PA, USA, in 1986. In 1992, he joined NASA’s Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, where he is currently the Director of the Center for Infrared Photodetectors. He is also a Senior Research Scientist and a Principal Member of the Engineering Staff with the NASA Jet Propulsion Laboratory.

Malin Premaratne earned several degrees from the University of Melbourne, including a B.Sc. in mathematics, a B.E. in electrical and electronics engineering (with first-class honors), and a PhD in 1995, 1995, and 1998, respectively. Currently, he is a full professor at Monash University Clayton, Australia. His expertise centers on quantum device theory, simulation, and design, utilizing the principles of quantum electrodynamics.

Journal information: APL Quantum