Category: HZDR

How electrons actually behave in warm dense matter

How electrons actually behave in warm dense matter

Widely used models mispredict collective electron oscillations in warm dense aluminium, study shows

Researchers at European XFEL, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Rostock University and other collaborating institutions have used high-precision experiments to demonstrate that the most widely used models for the behaviour of electrons in warm dense matter are inaccurate. Warm dense matter is challenging to study but also of key importance for a plethora of research, including the investigation of planetary interiors, material science, and laser fusion experiments. The study has been published in Physical Review Letters. 

In warm dense matter, electron density oscillates. The collective oscillations are called plasmons. They carry important information and can be observed using X-rays, resulting in scattering spectra – abstract images captured by a detector. In many experiments, these spectra are interpreted using simplified uniform electron gas models. However, the new measurements show that, for warm dense aluminium, these models consistently overestimate the plasmon energy by up to about 25 per cent (about 8 electronvolts) and fail to reproduce the full measured shape of the signal.

“Our measurements are precise enough to clearly distinguish between competing models,” says Thomas Preston of European XFEL. “That is important because these models are widely used to diagnose extreme states of matter. If the model is incorrect, that leads to inaccurately inferred properties.” The electron behaviour affects predictions of opacity, optical properties, electrical conductivity, and energy transport, for instance.

Read more on the European XFEL website

Image: Experimental setup at the HED-HIBEF instrument

Credit: European XFEL

Magnetic cooling – using a frustrated desert mineral

Magnetic cooling – using a frustrated desert mineral

The emerald-green mineral atacamite, named for the place it was first found, the Atacama Desert in Chile, gets its characteristic coloring from the copper ions it contains. These ions also determine the material’s magnetic properties: they each have an unpaired electron whose spin gives the ion a magnetic moment – comparable to a tiny needle on a compass. “The distinct feature of atacamite is the arrangement of the copper ions,” explains Dr. Leonie Heinze of Jülich Centre for Neutron Science (JCNS). “They form long chains of small, linked triangles known as sawtooth chains.” This geometric structure has consequences: although the copper ions’ spins always want to align themselves antiparallel to one another, the triangular arrangement makes this geometrically impossible to achieve completely. “We refer to this as magnetic frustration,” continues Heinze. As result of this frustration, the spins in atacamite only arrange themselves at very low temperatures – below 9 Kelvin (−264°C) – in a static alternating structure.

When the researchers examined atacamite under the extremely high magnetic fields at HZDR’s High Magnetic Field Laboratory (HLD), something surprising emerged: the material exhibited a noticeable cooling in the pulsed magnetic fields – and not just a slight one, but a drop to almost half of the original temperature. This unusually strong cooling effect particularly fascinated the researchers, as the behavior of magnetically frustrated materials in this context has scarcely been studied. However, magnetocaloric materials are considered a promising alternative to conventional cooling technologies, for example for energy-efficient cooling or the liquefaction of gases. This is because, instead of compressing and expanding a coolant – a process that takes place in every refrigerator – they can be used to change the temperature by applying a magnetic field in an environmentally friendly and potentially low-loss approach.

What is the origin of this strong magnetocaloric effect?

Additional studies at various labs of the European Magnetic Field Laboratory (EMFL) provided more in-depth insights. “By using magnetic resonance spectroscopy, we were clearly able to demonstrate that the magnetic order of atacamite is destroyed when a magnetic field is applied,” explains Dr. Tommy Kotte, a scientist at HLD. “This is unusual as the magnetic fields in many magnetically frustrated materials usually counteract the frustration and even encourage ordered magnetic states.”

The team found the explanation for the mineral’s unexpected behavior in complex numerical simulations of its magnetic structure: while the magnetic field aligns the copper ions’ magnetic moments on the tips of the sawtooth chains along the field and thus reduces the frustration as expected, it is precisely these magnetic moments that mediate a weak coupling to neighboring chains. When this is removed, a long-range magnetic order can no longer exist. This also provided the team with an explanation for the particularly strong magnetocaloric effect: it always occurs when a magnetic field influences the disorder – or more precisely, the magnetic entropy – of a system. In order to compensate for this rapid change in entropy, the material has to adjust its temperature accordingly. This is the very mechanism the researchers have now managed to demonstrate in atacamite.

Read more om HZDR website

Image: Artistic representation of the magnetic sawtooth structure of atacamite: The magnetic moments (green) of the Cu ions (white and blue) cannot be completely aligned antiparallel to each other due to the triangular arrangement. At low temperatures, this results in the compromise arrangement shown. An external magnetic field destroys it and leads to an unexpectedly strong magnetocaloric effect, which could be used for efficient cooling.

Credit: B. Schröder/HZDR

Structure of liquid carbon measured for the first time

Structure of liquid carbon measured for the first time

With the declared aim of measuring matter under extreme pressure, an international research collaboration headed by the University of Rostock and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) used the high-performance laser DIPOLE 100-X at European XFEL for the first time in 2023. With spectacular results: In this initial experiment they managed to study liquid carbon – an unprecedented achievement, as the researchers report in the journal Nature (DOI: 10.1038/s41586-025-09035-6). 

Liquid carbon can be found, for example, in the interior of planets and plays an important role in future technologies like nuclear fusion. To date, however, only very little was known about carbon in its liquid form because in this state it was practically impossible to study in the lab: Under normal pressure carbon does not melt but immediately changes into a gaseous state. Only under extreme pressure and at temperatures of approximately 4,500 degrees Celsius – the highest melting point of any material – does carbon become liquid. No container would withstand that.

Laser compression, on the other hand, can turn solid carbon into liquid for fractions of a second. And the challenge was to use these fractions of a second to take measurements. In a previously unimaginable way, this has now become reality at the European XFEL, the world’s largest X-ray laser with its ultrashort pulses, in Schenefeld, near Hamburg.

Unique measuring technology in this combination

The unique combination of the European XFEL with the high-performance laser DIPOLE100-X was crucial for the success of the experiment. It was developed by the British Science and Technology Facilities Council and made available to scientists from all over the world by the HIBEF User Consortium (Helmholtz International Beamline for Extreme Fields). A community of leading international research institutions at the HED-HIBEF (High Energy Density) experimental station at European XFEL has now combined powerful laser compression with ultrafast X-ray analysis and large-area X-ray detectors for the first time.

In the experiment, the high-energy pulses of the DIPOLE100-X laser drive compression waves through a solid carbon sample and liquefy the material for nanoseconds, that is, for a billionth of a second. During this nanosecond, the sample is irradiated with the ultrashort X-ray laser flash of the European XFEL. The carbon atoms scatter the X-ray light – similar to the way light is diffracted by a grating. The diffraction pattern allows inferences to be drawn about the current arrangement of the atoms in the liquid carbon.

The whole experiment only lasts a few seconds but is repeated many times: every time with a slightly delayed X-ray pulse or under slightly different pressure and temperature conditions. Many snapshots combine to make a movie. Researchers have thus been able to trace the transition from solid to liquid phase one step at a time.

Read more on European XFEL website

Image: Groundbreaking experiment at European XFEL: Research team measured structure of liquid carbon for the first time

Credit: Martin Kuensting / HZDR

Critical raw materials from electrolysers back into the cycle

Critical raw materials from electrolysers back into the cycle

Researchers succeed in recycling functional materials for hydrogen production

Hydrogen plays a central role in the energy transition. The gas is mainly produced with the help of electrolysers. This process requires critical raw materials such as platinum group metals, rare earths or nickel as catalysts. Researchers at the Helmholtz Institute Freiberg for Resource Technology (HIF), an institute of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), have now been able to recover these functional materials using innovative flotation processes and liquid-liquid particle separation, thus returning them to the material cycle. The research is part of the H2Giga lead project of the German Federal Ministry of Education and Research (BMBF), which is investigating the longevity and recyclability of hydrogen electrolysers.

Hydrogen is considered a clean energy source that can help reduce CO2 emissions. The focus here is particularly on green hydrogen, which is produced through the electrolysis of water using renewable energies such as wind and solar power. Hydrogen is used in industry, for example as a raw material for the production of chemicals and steel, as well as in the transport sector, where it is used as a fuel for fuel cell vehicles. Hydrogen can also be used to store surplus energy from renewable sources, making it an important building block for a sustainable and climate-friendly energy future. According to the national hydrogen strategy, Germany is expected to need 95 to 135 terawatt hours of hydrogen in 2030.

Various processes can be used to produce hydrogen – one is water electrolysis: water is broken down into hydrogen and oxygen using an electric current. The catalysts in the electrolyser consist of critical metals, the so-called functional materials. Proton exchange membrane electrolysers (PEM) mainly use metals from the platinum group, such as platinum, iridium and palladium. High-temperature electrolysers use rare earths and nickel. These critical raw materials need to be secured. This is a project that HIF researchers are working on under the leadership of the TU Bergakademie Freiberg in the ReNaRe project.

ReNaRe stands for Recycling – Sustainable Resource Utilization and is part of the H2Giga flagship project. To implement the national hydrogen strategy, the BMBF has set up three flagship projects for Germany’s entry into the hydrogen economy. One of these is H2Giga, which focuses on the series production of hydrogen electrolysers. ReNaRe concentrates on the end of life of electrolysers in order to return the materials used, and in particular the critical metals, to the material cycle.

“We are involved in the recycling of PEM and high-temperature electrolysers, as they are easy to dismantle. We use ultra-fine particle separation techniques to recover the functional materials. This is because the critical anode and cathode materials are present as fine particles. Their size corresponds to approximately one hundredth of a human hair. Liquid-liquid particle separation and agglomeration flotation have proven to be suitable for separating the functional materials. The extraction of ultrafine particles uses a sustainable solvent-water circulation system for the effective separation of hydrophobic, i.e. water-repellent cathode catalysts and hydrophilic (water-attracting) anode catalysts. The complementary agglomeration flotation uses an innovative, sustainable hydrophobic binder to enable agglomeration of the particles into a uniform mass. The binder is based on a special emulsion technology, i.e. an oil-water mixture with a very high water content, which selectively agglomerates hydrophobic ultrafine particles. This enables the separation of hydrophilic ultrafine particles by adhesion to gas bubbles and discharge in the foam,” says Sohyun Ahn, PhD student at the HIF, describing the procedure. “With both processes, we were able to recover up to 90 percent of the critical functional materials and return them to the material cycle. An important step towards operating hydrogen electrolysis economically and sustainably.”

Read more on HZDR website

Image: Water drop (black) above a hydrophobic particle (grey are at the bottom)

Source: Ahn, Sohyun

Concept for self-sustained oxygen mask wins competition

Concept for self-sustained oxygen mask wins competition

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have developed a concept for a self-sustained oxygen mask that uses the ability of microalgae to convert carbon dioxide into oxygen. This could form the basis for a portable microalgae-biomaterial hybrid device that enables prolonged oxygen supply and water absorption. With this concept, the HZDR team is one of the winners in a competition organized by the journal Nature Reviews Bioengineering. The task was to develop medical innovations for resource-limited regions.  

Life-saving medical devices such as oxygen masks are often dependent on limited or expensive resources, such as medical oxygen. In addition, many important devices and treatments require expensive and complex components, which hinders their development and local manufacturing. Solutions that work in resource-poor and disadvantaged regions of the world are, therefore, urgently needed. This is why the journal Nature Reviews Bioengineering has called on young bioengineers to find a simple solution to this problem.

Oxygen masks are usually dependent on an external oxygen supply, whether in the form of oxygen tanks or capsules. For the competition “The ultimate bioengineering challenge”, Xuan Peng, Xinne Zhao and Željko Janićijević from the Department of Nano-Microsystems for Life Sciences at HZDR´s Institute of Radiopharmaceutical Cancer Research have designed the idea for a self-sustained oxygen mask made of lightweight, biocompatible materials that enables prolonged oxygen supply and water collection in resource-poor areas.

The main challenge in designing a self-sustained oxygen mask was to reduce carbon dioxide and water vapor while increasing the oxygen content in the inhaled air. The scientists’ idea is based on photosynthesis, in which light energy (from the Sun) is converted into chemical energy. This energy is then used to build up energy-rich organic substances from carbon dioxide and water and release oxygen. For photosynthesis, they use microalgae, which are considered excellent converters of carbon dioxide to oxygen and can survive even under harsh environmental conditions. 

Read more on HZDR website

Image: Schematic illustration of how a self-sustained oxygen mask works.

Credit: HZDR / A. Grützner

A lighter, smarter magnetoreceptive electronic skin

A lighter, smarter magnetoreceptive electronic skin

Novel e-skins unlock a new level of interaction between humans and machines

Imagine navigating a virtual reality with contact lenses or operating your smartphone under water: This and more could soon be a reality thanks to innovative e-skins. A research team led by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has developed an electronic skin that detects and precisely tracks magnetic fields with a single global sensor. This artificial skin is not only light, transparent and permeable, but also mimics the interactions of real skin and the brain, as the team reports in the journal Nature Communications

Originally developed for robotics, e-skins imitate the properties of real skin. They can give robots a sense of touch or replace lost senses in humans. Some can even detect chemical substances or magnetic fields. But the technology also has its limits. Highly functional e-skins are often impractical because they rely on extensive electronics and large batteries. “Previous technologies have used numerous individual sensors and transistors to localize sources of a magnetic field, similar to touch sensors in a smartphone display. Our idea was to develop a more energy-efficient system that is more akin to our soft human skin and thus better suited for humans,” says Denys Makarov from the Institute of Ion Beam Physics and Materials Research at HZDR.

Lighter, more flexible, smarter

The researchers therefore replaced rigid, bulky substrates that usually host electronics with a thin, light, and flexible membrane that is just a few micrometers thick. The entire membrane is optically transparent and perforated, making the artificial skin permeable to air and moisture, allowing the real skin underneath to breathe.

However, such an ultra-thin membrane can accommodate a limited amount of electronic components. This is why novel e-skins feature a magnetosensitive functional layer, which acts as a global sensor surface to precisely localize the origin of magnetic signals. Since magnetic fields alter the electrical resistance of the material, a central analysis unit is able to calculate the signal location based on these changes. This not only emulates the functioning of real skin but also saves energy.

Artificial skin for a near-human sensory experience

“Such large-area magnetosensitive smart skins are a novelty,” says Pavlo Makushko, PhD student at HZDR and first author of the study. “Conceptually, e-skins now work more like the human body. No matter where I touch real skin, the signal always travels though nerves to the brain, which processes the signal and registers the point of contact. Our e-skins also have a single global sensor surface – just like our skin. And one single central processing unit reconstructs the signal – just like our brain.

This is made possible by tomography, a method that is also used for medical MRI or CT scans. It reconstructs the position of a signal from a large number of individual images. This technology is new for e-skins with magnetic field sensors – it was previously considered too insensitive for a low signal contrast of conventional magnetosensitive materials. The fact that we validated this method experimentally is a major technical achievement of the work, as Makushko emphasizes.

Read more on HZDR website

Image: Transparent magnetoreceptive e-skins for spatially continuous sensing over large areas.

Credit: Bild: P. Makushko / HZDR

Quantum heat dynamics toggled by magnetic fields

Quantum heat dynamics toggled by magnetic fields

Scientists discover unknown mechanism of heat conduction in quantum material

The ability to conduct heat is one of the most fundamental properties of matter, crucial for engineering applications. Scientists know well how conventional materials, such as metals and insulators, conduct heat. However, things are not as straightforward under extreme conditions such as temperatures close to absolute zero combined with strong magnetic fields, where strange quantum effects begin to dominate. This is particularly true in the realm of quantum materials. Researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), University of Bonn, and Centre national de la recherche scientifique (CNRS) now exposed the semimetal zirconium pentatelluride (ZrTe5) to high magnetic fields and very low temperatures. They found dramatically enhanced heat oscillations caused by a novel mechanism. This finding challenges the widely held belief that magnetic quantum oscillations should not be detectable in the heat transport of semimetals, as the scientists report in the journal PNAS.

The quantum material ZrTe5 belongs to the class of so-called topological semimetals. In physics, the term “topological” describes special materials that, due to their unique electronic structure, have extremely robust (“topologically protected”) conduction properties. In such materials, quantum effects can lead to unconventional and often bizarre phenomena that could play a crucial role in advancing future quantum technologies. Notably, both research and industry are currently investing considerable effort into developing quantum computers, with topological materials emerging as a promising avenue for their realization. Like ZrTe₅: it combines a rare set of non-trivial electronic properties, making it potentially relevant for high-precision electronics applications and magnetic-field sensor technologies.

“When a normal metal such as silver or copper is placed in strong magnetic fields at temperatures close to absolute zero, that is −273.15 °C, its heat conduction is expected to oscillate − a striking example of quantum mechanical dynamics of electrons in metals. This effect arises due to the existence of the so-called Fermi surface, a boundary between occupied and unoccupied energy states of electrons in a metal”, Dr. Stanisław Gałeski, currently assistant professor at Radboud University and visiting scientist at the Dresden High Magnetic Field (HLD) laboratory at HZDR, explains. “On the other hand, in semimetals, there are very few electrons available to transport heat, and as such, heat conduction is widely believed to be dominated by phonons − emergent particles that represent crystal lattice vibrations. As such, quantum oscillations should not be detectable in the transport of heat”, Gałeski sums up more traditional expectations. However, several recent experiments have found giant quantum oscillations in the heat conduction of semimetals, questioning the mechanism of heat transport.

Read more on HZDR website

Image: Artistic visualization of a crystalline rod made of the semimetal ZrTe5. There is a heat gradient from one end to the other. In its center, giant oscillations in its heat conduction are toggled by the magnetic field, which is generated by the electromagnet below.

Credit: B. Schröder/HZDR

Anomaly in the deep sea

Anomaly in the deep sea

Beryllium-10, a rare radioactive isotope produced by cosmic rays in the atmosphere, provides valuable insights into the Earth’s geological history. A research team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in collaboration with the TUD Dresden University of Technology and the Australian National University (ANU), has discovered an unexpected accumulation of this isotope in samples taken from the Pacific seabed. Such an anomaly may be attributed to shifts in ocean currents or astrophysical events that occurred approximately 10 million years ago. The findings hold the potential to serve as a global time marker, representing a promising advancement in the dating of geological archives spanning millions of years. 

Radionuclides are types of atomic nuclei (isotopes) that decay into other elements over time. They are used to date archaeological and geological samples, with radiocarbon dating being one of the most well-known methods. In principle, radiocarbon dating is based on the fact that living organisms continuously absorb the radioactive isotope carbon-14 (14C) during their lifetime. Once an organism dies, the absorption ceases, and the 14C content starts to decrease through radioactive decay with a half-life of approximately 5,700 years. By comparing the ratio of unstable 14C to stable carbon-12 (12C), researchers can determine the date of the organism’s death.

Archaeological finds, such as bones or remnants of wood, can be dated quite accurately in this way. “However, the radiocarbon method is limited to dating samples no more than 50,000 years old,” explains HZDR physicist Dr. Dominik Koll. “To date older samples, we need to use other isotopes, such as cosmogenic beryllium-10 (10Be).” This isotope is created when cosmic rays interact with oxygen and nitrogen in the upper atmosphere. It reaches the Earth through precipitation and can accumulate on the seabed. With a half-life of 1.4 million years, 10Be decays into boron, allowing geological dating that can extend back over 10 million years.

Conspicuous accumulation of beryllium

Some time ago, Koll’s research group examined unique geological samples retrieved from the Pacific Ocean at a depth of several kilometers. The samples consisted of ferromanganese crusts, primarily composed of iron and manganese, which had formed slowly but steadily over millions of years. To date the samples, the team analyzed the 10Be content using a highly sensitive method – Accelerator Mass Spectrometry (AMS) at HZDR. In this process, the sample is chemically purified before undergoing analysis for trace isotopes. Individual atoms from the sample are accelerated by high voltage, deflected by magnets, and then registered by specialized detectors. This method allows for the precise identification of 10Be, distinguishing it from other beryllium isotopes as well as molecules and isotopes with the same mass, such as boron-10.

When the research group evaluated the collected data, they were in for a surprise. “At around 10 million years, we found almost twice as much 10Be as we had anticipated,” reports Koll. “We had stumbled upon a previously undiscovered anomaly.” To eliminate any possibility of contamination, the experts analyzed additional samples from the Pacific, which also exhibited the same anomaly. This consistency allows the team to conclude that it is indeed a real phenomenon.

Read more on HZDR website

Image: Schematic depiction of production and incorporation of cosmogenic 10Be into ferromanganese crusts. A pronounced anomaly in 10Be concentration about 10 million years ago was discovered. This anomaly has great potential as time marker for the Late Miocene.

Credit: HZDR / blrck.de

The raw material detectives

The raw material detectives

New modeling methods and geochemical analyses provide information about deep deposits

The growing demand for raw materials makes mining unavoidable. The exploration of deposits increasingly relies on more environmentally friendly methods. In the European DeepBEAT project, scientists at the Helmholtz Institute Freiberg for Resource Technology (HIF), an institute of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), are pursuing the approach of using geochemical analyses to detect deep-seated ore deposits in a non-invasive manner. The researchers are testing the methods in three areas in Germany, the Czech Republic and Finland. The integrative involvement of all participants is an essential part of the project in order to improve mutual understanding in exploration projects. The EU is funding the three-year project with five million euros.

Our high-tech lifestyle is causing the raw materials consumption to rise continually. Despite intensive research into more effective processes, the demand cannot be met by recycling alone. At the same time, there is a growing awareness of our geopolitical responsibility regarding raw materials extraction. Both of these factors lead to the realization that raw materials must increasingly be extracted from European sources in a socially and environmentally responsible manner. New methods are needed to detect raw material-rich deposits in Europe – especially for deep-seated deposits, as neither geophysical nor geochemical signals from deep layers are easily distinguishable from signals close to the surface. To this end, scientists from six countries have joined forces to apply geochemical analysis methods for exploration and implement new forms of modeling in the European research project DeepBEAT (Deep exploration BoostEd by Advanced exploration Technologies).

Search for deep-seated deposits using geochemistry

Geochemistry is an important tool for many geoscientific questions. It provides insights into the material composition, distribution, stability, and cycle of chemical elements and their isotopes in minerals, rocks, soils, water, the Earth’s atmosphere, and the biosphere. “In geological exploration, geochemical approaches are typically used to analyze core samples in order to interpret information from depth. In the case of surface samples, geochemistry is traditionally applied to soil samples to detect, for example, abnormally high metal concentrations in soils. This typically only identifies near-surface ore deposits. Geochemical methods have been tested in a few studies to detect deeper deposits, and these have shown promising results,” explains Dr. Solveig Pospiech, project leader at HIF.

The detection of deep deposits is complicated by the distance between the surface and the ore body as a signal source. The challenge is to provide effective methods for improving the signal-to-noise ratio. These methods are intended to distinguish whether a measured signal originates from nearby sources – for example from outcropping rock or contamination from industrial activities – or from a deep source – i.e. a potential deposit. By tracing underground material cycles, scientists are gaining a better understanding of the geological situation. A key factor is selecting meaningful sampling points in the field and the materials to be sampled.

Read more on HZDR website

Image: Deep Exploration of concealed, deep-seated deposits of rare earth elements, cobalt and lithium boosted by advanced exploration technologies with geochemical methods at the surface

Credit: HZDR/Blaurock

Green cement: Electric heating to contribute to climate neutrality

Green cement: Electric heating to contribute to climate neutrality

HZDR researchers involved in research project on decarbonization of the cement industry

The cement industry is one of the largest producers of carbon dioxide. It is responsible for up to eight percent of global man-made emissions – almost three times as much as the global air traffic. To reduce this share and become climate-neutral, the industry is relying on technological innovations. The international project “ECem”, in which scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) are also involved, is pursuing a promising approach. With the help of electric heating technologies for the energy-intensive process of calcination, the partners from science and industry want to drastically reduce CO2 emissions in cement production. The project started in the fall of 2024 and will run for three and a half years. It is funded by the Innovation Fund Denmark with 21 million Danish crowns (about 2.8 million euros).

Calcination is one of the most important process steps in the production of cement. Limestone is heated to approximately 1450°C in a large furnace and converted into clinker, the main component of cement, by thermal decomposition. This chemical process is responsible for a large proportion of the CO2 emissions released by the cement industry as a whole. Two-thirds of the CO2 is produced during the decomposition of the limestone, a process known as decarbonization, and is therefore unavoidable. The remaining third is due to the enormous energy consumption required to reach the high temperatures. Fossil fuels such as coal or gas are usually used for this purpose.

The „ECem“ (Electric calciner technologies for cement plants of the future) research project is now taking on this industrial heating process. The goal is to develop a more climate-friendly alternative. To this end, the project partners, led by the Danish cement company FLSmidth, including the Danish Institute of Technology, the University of Aalborg, the companies European Energy and Cementos Argos, as well as the HZDR, want to develop two different electric heating technologies.

Metal balls give limestone the necessary material properties

While the Danish partners in the project are working on the development of an infrared radiant heating system, scientists at the HZDR Institute for Fluid Dynamics are researching an electrical solution based on inductive heating. The team first wants to set up a laboratory experiment in which induction coils generate a high-frequency field to heat the material in a container. In a later stage, a rotating kiln will be modeled in a further experimental setup with key data that closely approximates industrial conditions. The challenge is that materials such as limestone, which consists mainly of calcium carbonate, are actually unsuitable for induction heating due to their poor electrical conductivity.

To overcome this obstacle, the team wants to mix so-called susceptors into the raw material to be heated. These are components designed to efficiently convert the electric energy into heat and transfer it to the material. An important task is to find the right material that can function robustly as a susceptor at high temperatures and under harsh industrial conditions. Possible candidates must have a high melting point, must not react with the limestone and should be abrasion-resistant. Forming the susceptors into a shape, for example as metal balls, would have the advantage of combining the calcination and grinding processes into a single step. Investments in the electrification of industrial processes could, in addition to avoiding CO2, have further positive effects such as increasing efficiency or improving product quality, thus giving the respective companies a competitive advantage in the global markets. 

Read more on HZDR website

Image: Functional diagram of the inductive heating of a rotary kiln reactor in cement production: so-called susceptors are added to compensate for the poor electrical conductivity of the raw material. These components, shaped as metal balls in the picture, efficiently convert the energy transferred by induction into heat and distribute it evenly throughout the vessel.

Source: HZDR / B.Schröder

Quantum computers in silicon

Quantum computers in silicon

Development of a new European quantum technology begins

The EQUSPACE consortium (Enabling New Quantum Frontiers with Spin Acoustics in Silicon) has received 3.2 million euros from the European Innovation Council’s (EIC) Pathfinder Open funding program to advance the development of silicon-based quantum technologies. In addition to the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the project brings together four other partners from three EU countries and convenes experts from the fields of spin qubits, optomechanics and atomic silicon modifications to develop a novel silicon-based quantum platform.

Although silicon is the central material for classic computers, it does not play a key role in the currently favored quantum computer concepts. However, it would make a lot of sense to use the multi-billion euro silicon infrastructure already developed with semiconductor technology to process qubits – the quantum mechanical information units. Researchers have shown that so-called donor spin qubits are actually particularly well suited for this endeavor. These qubits use a property of impurity atoms, their spin, to process information. Compared to other quantum systems, they are characterized by long periods of time over which they remain stable in order to perform quantum mechanical computing operations. Currently, however, they are not the workhorse of commercial quantum computers, as there are no suitable coupling and readout mechanisms that could be used to scale them up to a practically usable level.

EQUSPACE now aims to create a long-term future for silicon-based donor spin qubits in Europe. The platform makes an effort to connect the qubits, which are based on tiny atomic spins, via sound waves in vibrating structures. Lasers and single-electron transistors will also be used to electrically read out the result at the end of the quantum mechanical calculation. The project seeks to provide a scalable solution for all important aspects of a quantum platform: the control and readout of the result, the spin-spin coupling between qubits, and the transmission of quantum information between computing units on the chip. The final outcome could be a complete quantum information platform that includes qubits, interconnects and scalable control and readout electronics.

HZDR expertise in silicon quantum technology

A team from the Institute of Ion Beam Physics and Materials Research at HZDR will contribute its expertise in the atomic modification of silicon for quantum applications and further develop the materials science methods required as a basis for the project. The team will use a focused ion beam to locally enrich ultra-pure silicon with the isotope silicon-28. Compared to many other materials, silicon-28 has the advantage that its atomic nuclei have no spin that could interact with magnetic fields or the spin of other particles and thus interfere with the calculations. “Through the targeted enrichment with special isotopes, the quantum state remains stable for longer timespans. This allows more complex quantum operations, and the platform could thus outperform classical computers and other quantum computer systems in the future,” says HZDR project manager Dr. Nico Klingner.

In addition to isotope purification, the team is developing the single-ion implantation of donor atoms. The aim is to implant individual bismuth atoms whose spin forms a two-state system that can point either “up” or “down”. The special feature of qubits is that at very low temperatures, both states can exist simultaneously in superpositions: the spin can be in a combination of the “up” and “down” states at the same time. This allows quantum computers to perform many calculations in parallel, which can drastically increase their computing power.

One of the main advantages of donor spin qubits is their relative stability compared to other types of qubits, for example those based on superconducting circuits. The spin in a donor atom is less susceptible to perturbations from the environment, so the quantum state can be maintained over longer periods of time. This stability is essential for scaling quantum computers to a larger number of qubits without losing coherence or precision of computations. “These contributions from HZDR, especially in the areas of isotope purification, implantation and strain engineering in semiconductors, are fundamental to the success of the EQUSPACE project,” states Professor Juha Muhonen, the coordinator of the project.

Read more on HZDR website

Image: In the single ion implanter TIBUSSII (Triple Ion Beam UHV System for Single Ion Implantation), individual dopants can be implanted atom by atom into a material, for example to generate qubits.

Credit: B. Schröder / HZDR

How plant communities change when conquering uninhabited ground

How plant communities change when conquering uninhabited ground

New mathematical model by CASUS researcher explains the different interactions of pioneer plants with other plants over time

Some plants are able to take over uninhabited spaces like sand dunes, volcanic substrates and rockfall areas. The first colonizers have specific traits that allow them to grow in such hostile environments. Other plants lack such traits but will soon follow these pioneers. Ricardo Martínez-García from the Center for Advanced Systems Understanding (CASUS), an institute of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), and collaborators from Spain and Brazil investigated the type of interaction between different species on these newly conquered grounds with the help of a mathematical model based on existing root physiology knowledge. Their new model connects the type of species interaction with the general availability of a scarce soil resource. It also reveals the best strategy for the pioneer who can harness a resource that is not freely available.

Plants interact in many different ways and very often we see that one individual is supporting another from a different species. The term experts use for that is facilitation. With symbiotic facilitation, both plants support each other. With commensalistic facilitation, the nurtured plant neither affects its benefactor positively nor negatively. The third type of facilitation is called antagonistic facilitation. Here, the nurtured partner benefits at the expense of the benefactor. The latter, for example, leaves a self-produced resource to the partner, even though he could actually use it himself. The benefactor appears to “accept” this situation: Neither a kind of defensive reaction against the removal of resources nor a complete halt to production can be observed.

“There is an ongoing debate about whether antagonistic facilitation actually exists. Our study provides a clear result: this type of interaction between plant species could occur in nature,” says Dr. Ricardo Martínez-García, CASUS Young Investigator and corresponding author of the study that will be published in the second October issue of the journal New Phytologist (DOI: 10.1111/nph.20053). “To prove antagonistic facilitation experimentally, requires a big effort. To begin with, it must be ruled out that this type of interaction is neither symbiotic nor commensalistic facilitation. In addition, it has to be shown that it is not a classic competition where both plants are harming each other in the fight for resources.”

Plants as miners

Martínez-García as well as Ciro Cabal (King Juan Carlos University, Madrid, Spain) and Gabriel A. Maciel (South American Institute for Fundamental Research, São Paulo, Brazil), the two lead authors of the study, focused with their modelling efforts on an example from nature where the existence of antagonistic facilitation had been suspected for a long time: pioneering plants starting to grow on uninhabited ground and other plants soon following track. Such pioneer plants can engineer their environment to increase the availability of certain scarce soil resources like nitrogen and phosphorus. Their abilities certainly help them thrive and they do not seem to be bothered by appearing opportunistic plants helping themselves at the buffet. The bottom line is that the pioneer still benefits from its special traits. From an experimental point of view, the pioneer plant example appears to be a manageable system. Nevertheless, practitioners have not yet been able to determine the type of interaction for this example with certainty. The results of the model presented here are now a strong argument for the existence of antagonistic facilitation in these pioneer areas. Of course, it stands to reason that this type of interaction probably exists not only here, but also elsewhere in nature.

“Our model also shows that plant interactions are an emergent property of resource availability,” adds Cabal. “It turned out that in environments with low and intermediate resource availability antagonistic facilitation is the best strategy. This too was suggested some time ago but it was so far not backed by either experimental data or theoretical models.” Consequently, the research team was not only able to provide reliable results for the general existence of this type of interaction. In fact, antagonistic facilitation is even the optimal interaction between two plant communities under some environmental conditions.

As over time the soil changes and more and more plant species flourish, the interaction between the species changes. Although the pioneer species continue to increase the availability of resources, this no longer affects the other plants due to the generally good resource situation. The phase of antagonistic facilitation is over and all plants compete against each other. Further into the future, the mining capability of the pioneer will even become a burden in this competition. The pioneers are at a disadvantage. In the end, other plant species prevail in the competition and pioneer plants are no longer to be found on the site.

Read more on HZDR website

Image: Pioneer grasses conquer volcanic sand

Credit: Ruedi Haeberli/Unsplash

Flow research on the outskirts of space

Flow research on the outskirts of space

For years, various models have been developed to describe an important class of mixing effects that occur, for example, in the flow in a chemical reactor. Experimental validation, however, has lagged far behind due to the superimposition of gravity effects. A European research team involving the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and partners at the University of Szeged (Hungary) and Université libre de Bruxelles (ULB, Belgium) has now closed this gap with experiments conducted under weightlessness. The researchers recently published their results in the Nature journal npj Microgravity

So-called reaction-diffusion fronts occur when two chemicals react with one another and at the same time spread out. Scientists can use this effect to model and better understand problems in chemistry and physics as well as in completely different areas like the financial world or linguistics as the underlying mathematical equations have the same characteristics. It gets more complicated when researchers combine these reactions with flows. Processes of this kind are important for technological applications relating to combustion processes, geology, the production of specific materials and storing carbon dioxide. Despite the plethora of applications, essential parts of these systems are not yet fully understood.

“Up to now, experiments to verify models of such processes have been distorted by buoyancy effects caused by density differences between the reaction solutions. In order to isolate this problem, we conducted experiments using weightlessness on board of a sounding rocket. Our partners did parallel numerical simulations to show the importance of the two-dimensional effects that can’t be taken into account in simple one-dimensional models,” says Dr. Karin Schwarzenberger of HZDR’s Institute of Fluid Dynamics, outlining the work of her team.

Rocket take-off at the Arctic Circle

The experiment took place on 1 October 2022 – on board of the sounding rocket TEXUS-57 that was launched from the Esrange Space Center, 40 kilometers east of Kiruna in Sweden. The collaborative project involving Airbus Defense & Space, the European Space Agency ESA and the German Aerospace Center (DLR) transported, among other things, the Schwarzenberger team’s experimental model to the outskirts of space. The module had three reactors of different sizes consisting of glass plates stacked on top of each other at differing proximity. The rocket reached a height of 240 kilometers, achieving a state of almost complete weightlessness for nearly six minutes. During this period, the researchers were able to run their experiments automatically – experiments that resulted from several years of meticulous planning. The reaction was triggered when the weightlessness set in. Three high-resolution cameras filmed the reaction fronts that spread between two flowing liquids. It was these images that were the focus of all the team’s efforts: with their help, the researchers can now separate a very specific mixing effect from other flow phenomena.

Read more on HZDR website

Image : A reaction front spreads between two flowing liquids.

Credit: B. Schröder/HZDR

Real-Time Monitoring after Pancreatic Surgery

Real-Time Monitoring after Pancreatic Surgery

Complications after pancreatic surgery are common and can be life-threatening.  One of the most serious yet common complications is postoperative pancreatic fistula. This condition is diagnosed based on increased concentrations of the pancreatic enzyme alpha-amylase in drainage secretions. Currently, the analysis of these enzymes is routinely conducted on the first and third postoperative day. Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University Hospital Dresden (UKD) now report in the journal Biosensors and Bioelectronics (DOI: 10.1016/j.bios.2024.116034) on the development of a portable device that can carry out the enzyme determination continuously and in real time.

Up to thirty percent of patients undergoing partial resection of the pancreas suffer from postoperative pancreatic fistula, a complication resulting from leakage of pancreatic enzymes into the abdominal cavity. This condition can considerably prolong hospitalization and lead to a delay or non-administration of postoperative chemotherapy, which is an important component of pancreatic cancer treatment. Postoperative pancreatic fistula is diagnosed by examining the digestive enzyme alpha-amylase in drainage secretions by measuring its biochemical reaction with starch, a storage carbohydrate. The enzyme alpha amylase breaks down starch carbohydrate into its components. High alpha-amylase levels in the drain indicate postoperative pancreatic fistula. In current clinical practice, this test is carried out on the first and third day after surgery. It can take up to six hours until test results become available to caregivers. In addition, the current standard process only provides information on the patient’s condition at a specific point in time.

Development of a millifluidic device

As continuous monitoring of alpha-amylase is not yet feasible, the adjustment of medical treatment in the event of complications can be delayed. For this reason, Dr. Larysa Baraban at the HZDR’s Institute of Radiopharmaceutical Cancer Research, together with her team and colleagues from the Department of Visceral, Thoracic and Vascular Surgery at the University Hospital Dresden, have developed a portable, droplet-based millifluidic device that can measure the drainage fluid’s alpha-amylase activity in real time. This instrument is intended to monitor patients in the critical first days after surgery. Millifluidics means that fluids are passed through tubes of approximately one millimeter in diameter. A miniscule amount of drainage fluid is continuously collected from patient drainage samples and encapsulated into nanoliter-sized droplets with a starch reagent. The use of this microfluidic droplet format reduces the time between sampling and reading to one to two minutes.

To determine the strength of the reaction, Baraban and her team work with a fluorescent dye. The fluorescence increases with increasing concentrations of alpha-amylase. The more intense the dye, the higher the concentration of the alpha-amylase in the drainage secretion, which indicates the presence of postoperative pancreatic fistula. In clinical practice, such a finding could trigger follow-up examinations at an early stage, aiming to avoid deterioration of the complication in patients.

Read ore on HZDR website

Image: Dr. Larysa Baraban – Head of the Life Science Nanomicrosystems department

Credit: HZDR / Anja Schneider

Ultrafast and tunable

Ultrafast and tunable

Terahertz-to-visible light conversion for future telecommunications

A study carried out by a research team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Catalan Institute of Nanoscience and Nanotechnology (ICN2), University of Exeter Centre for Graphene Science, and TU Eindhoven demonstrates that graphene-based materials can be used to efficiently convert high-frequency signals into visible light, and that this mechanism is ultrafast and tunable, as the team presents its findings in Nano Letters (DOI: 10.1021/acs.nanolett.3c00507). These outcomes open the path to exciting applications in near-future information and communication technologies.

The ability to convert signals from one frequency regime to another is key to various technologies, in particular in telecommunications, where, for example, data processed by electronic devices are often transmitted as optical signals through glass fibers. To enable significantly higher data transmission rates future 6G wireless communication systems will need to extend the carrier frequency above 100 gigahertz up to the terahertz range. Terahertz waves are a part of the electromagnetic spectrum that lies between microwaves and infrared light. However, terahertz waves can only be used to transport data wirelessly over very limited distances. “Therefore, a fast and controllable mechanism to convert terahertz waves into visible or infrared light will be required, which can be transported via optical fibers. Imaging and sensing technologies could also benefit from such a mechanism,” says Dr. Igor Ilyakov of the Institute of Radiation Physics at HZDR.

Read more on the HZDR website

Image: A graphene-based material converts incoming terahertz pulses (from above) into visible light in an ultrafast and controllable manner – optimal for data transport in optical fibers.

Credit: B. Schröder/HZDR

Magnetic sandwich mediating between two worlds

Magnetic sandwich mediating between two worlds

Scientists couple terahertz radiation with spin waves

An international research team led by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has developed a new method for the efficient coupling of terahertz waves with waves of much shorter wavelengths, so-called spin waves. As the experts report in the journal Nature Physics (DOI:  10.1038/s41567-022-01908-1), their experiments, in combination with theoretical models, clarify the fundamental mechanisms of this process previously thought impossible. The results are an important step for the development of novel, energy-saving spin-based technologies for data processing.

“We were able to efficiently excite high-energy spin waves using terahertz light in a sandwich-like material system consisting of two metal films a few nanometers thick, with a ferromagnetic layer sandwiched in between,” says Dr. Sergey Kovalev of the Institute of Radiation Physics at HZDR, where the experiments were conducted. Electrons have an effective spin which behaves like a spinning top. And like a gyroscope, an external perturbation can tilt the spin’s axis of rotation: A gyroscopic motion, called precession, follows suit. In ferromagnetic materials, there is a very strong interaction between the electron spins, and as a result, a precession started locally continues in the form of a spin wave throughout the ferromagnetic material layer. This is interesting because a spin wave – like any wave – can be used as an information carrier.  While each electron spin is in motion, in the ferromagnets considered it remains in its position in the atomic lattice, therefore no current flow is involved. So, unlike in today’s computer chips, there are no heat losses due to currents in spin-based devices.

Read more on the HZDR website

Image: A terahertz light wave (from left) is converted into a spin wave (right) in a sample of thin metallic layers. In a heavy metal layer (left), electrical currents are first excited by the terahertz field. Within an ultrashort time, the spin Hall effect leads to the accumulation of spins with a certain orientation at the interface with a ferromagnetic layer (right). This directed spin current then triggers a coherent, nanomater-wavelength spin wave in the ferromagnetic material.

Credit: HZDR/Juniks