Physicists find unusual waves in nickel-based magnet

(Left) In nickel molybdate crystals made of two parts nickel, three parts molybdenum and eight parts oxygen, nickel ions are subject to both tetrahedral and octahedral crystalline environments, and the ions are locked in triangular lattices in each environment. (Right) Crystal electric field spin excitons from tetrahedral sites in nickel molybdate crystals form a dispersive, diffusive pattern around the Brillouin zone boundary, likely due to spin entanglement and geometric frustrations. Left and right halves of the image show different model calculations of these patterns.
Illustration Credit: Courtesy of Bin Gao/Rice University

Perturbing electron spins in a magnet usually results in excitations called “spin waves” that ripple through the magnet like waves on a pond that’s been struck by a pebble. In a new study, Rice University physicists and their collaborators have discovered dramatically different excitations called “spin excitons” that can also “ripple” through a nickel-based magnet as a coherent wave.

In a study published in Nature Communications, the researchers reported finding unusual properties in nickel molybdate, a layered magnetic crystal. Subatomic particles called electrons resemble miniscule magnets, and they typically orient themselves like compass needles in relation to magnetic fields. In experiments where neutrons were scattered from magnetic nickel ions inside the crystals, the researchers found that two outermost electrons from each nickel ion behaved differently. Rather than aligning their spins like compass needles, the two canceled one another in a phenomenon physicists call a spin singlet.

UC Irvine physicists discover first transformable nano-scale electronic devices

The golden parts of the device depicted in the above graphic are transformable, an ability that is “not realizable with the current materials used in industry,” says Ian Sequeira, a Ph.D. student who worked to develop the technology in the laboratory of Javiar Sanchez-Yamahgishi, UCI assistant professor of physics & astronomy.
Image Credit: Yuhui Yang / UCI

The nano-scale electronic parts in devices like smartphones are solid, static objects that once designed and built cannot transform into anything else. But University of California, Irvine physicists have reported the discovery of nano-scale devices that can transform into many different shapes and sizes even though they exist in solid states.

It’s a finding that could fundamentally change the nature of electronic devices, as well as the way scientists research atomic-scale quantum materials. The study is published this week in Science Advances.

“What we discovered is that for a particular set of materials, you can make nano-scale electronic devices that aren’t stuck together,” said Javier Sanchez-Yamagishi, an assistant professor of physics & astronomy whose lab performed the new research. “The parts can move, and so that allows us to modify the size and shape of a device after it’s been made.”

Methane from megafires: more spew than we knew

Sky filled with wildfire pollution in 2020.
Photo Credit: Frausto-Vicencio/UCR

Using a new detection method, UC Riverside scientists found a massive amount of methane, a super-potent greenhouse gas, coming from wildfires — a source not currently being accounted for by state air quality managers. 

Methane warms the planet 86 times more powerfully than carbon dioxide over the course of 20 years, and it will be difficult for the state to reach its required cleaner air and climate goals without accounting for this source, the researchers said. 

Wildfires emitting methane is not new. But the amount of methane from the top 20 fires in 2020 was more than seven times the average from wildfires in the previous 19 years, according to the new UCR study. 

“Fires are getting bigger and more intense, and correspondingly, more emissions are coming from them,” said UCR environmental sciences professor and study co-author Francesca Hopkins. “The fires in 2020 emitted what would have been 14 percent of the state’s methane budget if it was being tracked.” 

The state does not track natural sources of methane, like those that come from wildfires. But for 2020, wildfires would have been the third biggest source of methane in the state. 

X-rays Reveal Electronic Details of Nickel-based Superconductors

Yao Shen, a postdoctoral researcher at Brookhaven Lab and first author of two papers describing the electronic structure of a nickel-based superconductor, at the SIX beamline of the National Synchrotron Light Source II (NSLS-II) where the experiments were done.
Photo Credit: Brookhaven National Laboratory

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have discovered new details about the electrons in a nickel-based family of superconducting materials. The research, described in two papers published in Physical Review X, reveals that these nickel-based materials have certain similarities with—and key differences from—copper-based superconductors. Comparing the two kinds of “high-temperature” superconductors may help scientists zero in on key features essential for these materials’ remarkable ability to carry electrical current without losing energy as heat.

“The quest to understand high-temperature superconductors is a decades-old challenge,” said Mark Dean of Brookhaven Lab’s Condensed Matter Physics & Materials Science Department, who led the research described in both papers. Ever since copper-based, or cuprate, superconductors were discovered in the 1980s, scientists have been trying to understand what makes them tick.

The interest is driven in large part by their potential for energy-saving applications. Picture power lines that deliver electricity to homes far from wind and solar farms without losing a speck of energy, and computers and other devices that function flawlessly without the need for expensive and energy-intensive cooling.

How a photon becomes four charge carriers

Illustration of exciton cleavage in the organic semiconductor pentacene consisting of five benzene rings. Instead of the usually two free charge carriers, four free charge carriers, represented by orange orbits, are generated by absorbing a photon in pentacene.
Photo Credit: Technical University of Berlin

Some materials convert photons into more charge carriers than would be expected. With an ultra-fast film, researchers have now been able to get an idea of this process. Physicists from the University of Würzburg were there.

Photovoltaics, i.e. The conversion of light into electricity is a key technology in the sustainable generation of energy. Since Max Planck and Albert Einstein, it has been known that both light and electricity occur in tiny, quantized packages: on the one hand in the form of photons and on the other hand as elementary charges in the form of electrons and holes.

Better solar cells thanks to exciton splitting

In the material of a conventional solar cell, the energy of a single photon is transferred to two free charges, nothing more. However, some molecular materials such as pentacene show an exception to this rule and instead convert a photon into four charges. This excitation doubling, which is referred to as exciton fission, is of great benefit for the highly efficient photovoltaics, in particular to improve the prevailing technologies based on silicon.

Neutrons for better vaccines against multidrug resistant germs

Dr. Jia-Jheng Kang prepares measurements for the vaccines at the KWS-2 sample site.
Photo Credit: Bernhard Ludewig, FRM II / TUM

Neutrons from the Research Neutron Source Heinz Maier-Leibnitz (FRM II) can be used to explore the structure of biomolecules. The most recent success: the precise analysis of a promising vaccine against multidrug resistant germs.

Bacteria which are resistant to all conventional antibiotics cause more than a million deaths each year. Consequently, researchers around the world are searching for new therapeutic approaches to combat these pathogens. Two years ago, an international team in Grenoble identified an active ingredient suitable for the production of a vaccine against multidrug resistant bacteria Pseudomonas aeruginosa. The vaccine has in the meantime been successfully tested on mice.

"As with many new vaccines, in this case the active ingredient is embedded in liposomes. The exact characterization and understanding of these nanoscopic biomolecules is a key factor in the development and optimization of future vaccines," says Dr. Marco Maccarini, biophysicist at the French National Centre for Scientific Research (CNRS). Together with experts at the TIMC laboratory of the Université Grenoble Alpes (UGA) and at the FRM II he has successfully analyzed the structure of the candidate vaccine against Pseudomonas aeruginosa.

Ultrasmall swirling magnetic vortices detected in iron-containing material

Simulation capturing the different swirling textures of skyrmions and merons observed in ferromagnet thin film.
Image Credit: University of Edinburgh/based on microscopy images collected by Argonne on samples prepared at MagLab

Microelectronics forms the foundation of much modern technology today, including smartphones, laptops and even supercomputers. It is based on the ability to allow and stop the flow of electrons through a material. Spin electronics, or spintronics, is a spinoff. It is based on the spin of electrons, and the fact that the electron spin along with the electric charge creates a magnetic field.

“This property could be exploited for building blocks in future computer memory storage, brain-like and other novel computing systems, and high-efficiency microelectronics,” said Charudatta Phatak, group leader in the Materials Science division at the U.S. Department of Energy’s (DOE) Argonne National Laboratory.

A team including researchers at Argonne and the National High Magnetic Field Laboratory (MagLab) discovered surprising properties in a magnetic material of iron, germanium and tellurium. This material is in the form of a thin sheet that is only a few to 10 atoms in thickness. It is called a 2D ferromagnet.

The team discovered that two kinds of magnetic fields can coexist in this ultrathin material. Scientists call them merons and skyrmions. They are like miniature swirling storm systems dotting the flat landscape of the ferromagnet. But they differ in their size and swirling behavior.

Tur­bu­lence: Decades-old the­ory gets a major remake

Ivana Stiperski and the students from the Field Course in Alpine Meteorology setting up the instruments at the “Hochhäuser” i-Box station in the Inn Valley.
Photo Credit: Tobias Posch

Turbulence plays an essential role in weather and climate, and correctly representing its effects in numerical models is crucial for accurate weather forecasts and climate projections. However, the theory describing the effect of turbulence has not changed since its conception in 1950s, despite the fact that it is not representative for the majority of the Earth’s land surface, especially over mountains and polar regions. The Innsbruck meteorologist Ivana Stiperski has now extended the turbulence theory to complex atmospheric conditions. The researcher thus paves the way for the first generalized turbulence theory over complex terrain.

Turbulence is the most important exchange mechanism between the Earth's surface and the overlying atmosphere. However, this mechanism remains one of the last great puzzles of classical physics and mathematics. Ivana Stiperski, head of the research group "Atmospheric Turbulence" at the Department of Atmospheric and Cryospheric Sciences at the University of Innsbruck, has dedicated her work to the study of turbulence over mountains, and since 2020 her team is working on the topic within the framework of an ERC Consolidator Grant. "Turbulence affects phenomena as diverse as climate, storm systems, air pollution and glacier melt. Accurate weather forecasts and climate predictions therefore require a precise description of turbulence, and over the complex terrain of mountainous regions this is particularly difficult as very little is known about how complex terrain modifies turbulence, and no major advance has happened over the past 70 years", Stiperski explains. Until now, the understanding of atmospheric turbulence and how it is included in weather and climate models has been based on the so-called similarity theory, more specifically the "Monin-Obukhov similarity theory " first postulated in 1954. This decades-old theory of turbulence, however, assumes that the Earth’s surface is flat and horizontally homogeneous (i.e., has uniform characteristics in the horizontal, such as for example infinite grasslands or corn fields), and therefore it is not representative for the majority of the Earth’s land surface. This incorrect representation of turbulence adds uncertainty to weather prediction and climate projections.

Separated at last

In the new method, laser pulses of different power (green) are combined in such a way that single excitation (blue), double excitation (red) and triple excitation (yellow) can be distinguished, for example, in biological light-harvesting complexes.
Illustration Credit: Julian Lüttig / Universität Würzburg

Scientists at the Universities of Würzburg and Ottawa have solved the decades-old problem of distinguishing between single and multiple light excitations. They present their new method in the journal Nature.

The construction of the first laser in 1960 ushered in commercial applications with light that have become an integral part of our everyday lives. At the same time, this development opened up the scientific field of laser spectroscopy – a technique that is central to the analysis of materials and the study of fundamental physical phenomena.

Despite all the successes, however, research teams have struggled since the 1970s with the problem that a laser shining on a sample can excite it not just once, but several times per experiment. In this case, the measurement results of the single excitation and the multiple excitations overlap and usually cannot be separated, making it difficult to understand the material.

Pressure-Based Control Enables Tunable Singlet Fission Materials for Efficient Photoconversion

Applying hydrostatic pressure as an external stimulus, Tokyo Tech and Keio University researchers demonstrate a new way to regulate singlet fission (SF), a process in which two electrons are generated from a single photon, in chromophores, opening doors to the design of SF-based materials with enhanced (photo)energy conversion. Their method overrides the strict requirements that limit the molecular design of such materials by realizing an alternative control strategy.

Singlet fission (SF) is a process in which an organic chromophore (a molecule that absorbs light) in an excited singlet state transfers energy to a neighboring chromophore, resulting in two correlated triplet exciton pairs (pairs of bound electron-hole states, a "hole" signifying the absence of an electron) that decay to low energy triplet excitons. These excitons have long lifetimes and show efficient light emission, making SF promising for efficient light energy conversion.

However, the molecular design of SF-based materials is limited by the requirement that the energy of the excited singlet state must be at least equal to the energy of the two triplet states. One way to overcome this limit is by applying external stimuli, such as temperature or pressure, to manipulate the SF process.

Breakthrough on the way to the biological solar cell

Marc Nowaczyk which everted from the Ruhr University to the University of Rostock. The current works were partly made in Bochum.
Photo Credit: ITMZ University of Rostock

Researchers question the way photosynthesis works.

A research team from the University of Cambridge, the University of Rostock and the Ruhr University Bochum succeeded for the first time in obtaining electrons directly from the early stages of photosynthesis. This breakthrough questions the previous model for the basic functioning of photosynthesis and has the potential to revolutionize the development of solar cells based on biological catalysts. The research work was published in the renowned journal Nature from 22. Published March 2023.

Manufacture hydrogen with sunlight

Biological catalysts, so-called enzymes, have long since determined our everyday life. For example, they are used as additives in detergents, they refine food or are used in large-scale processes to produce medicines or raw materials for the chemical industry. Compared to chemical catalysts, they have the advantage that they only react with very specific raw materials and therefore produce very specific products. In addition, biological catalysts are never based on precious metals or other rare raw materials. "In nature, solutions have always been established that are not limited by the availability of raw materials," says Prof. Dr. Marc Nowaczyk, head of the chair for biochemistry at the University of Rostock and co-author of the study, who did part of the work at the Ruhr University Bochum as part of the graduate school Microbial Substrate Conversion, MiCon for short.

‘Neutron camera’ method captures atomic-scale activity in a flash

Artist’s conceptual drawing illustrates the novel energy filtering technique using neutrons that enabled researchers at ORNL to freeze moving germanium telluride atoms in an unblurred image. The images offered key insights into how the material produces its outstanding thermoelectric performance.
Illustration Credit: Jill Hemman/ORNL, U.S. Dept. of Energy

Scientists have long sought to better understand the “local structure” of materials, meaning the arrangement and activities of the neighboring particles around each atom. In crystals, which are used in electronics and many other applications, most of the atoms form highly ordered lattice patterns that repeat. But not all atoms conform to the pattern.

When some atoms take up local arrangements that are different than that implied by the overall structure of the crystal, studying the local structure gets more difficult — especially when the atoms are moving. In fact, the inability to clearly see these local effects means researchers are often not aware they can happen.

Now researchers using the Spallation Neutron Source at Oak Ridge National Laboratory have developed a new method of studying the local structure of materials in detail and in real time.

The team developed a variable-shutter pair distribution function, or vsPDF, technique in which neutrons function like a camera but at timescales that are a trillion times faster.

Purifying water with the power of the sun

A Notre Dame researcher’s invention could improve access to clean water for some of the world’s most vulnerable people.

 “Today, the big challenges are information technology and energy,” says László Forró, the Aurora and Thomas Marquez Professor of Physics of Complex Quantum Matter in the University of Notre Dame's Department of Physics and Astronomy. “But tomorrow, the big challenge will be water.”

The World Health Organization reports that today nearly 2 billion people regularly consume contaminated water. It estimates that by 2025 half of the world’s population could be facing water scarcity. Many of those affected are in rural areas that lack the infrastructure required to run modern water purifiers, while many others are in areas affected by war, natural disasters or pollution. There is a greater need than ever for innovative ways to extend water access to those living without power, sanitation and transportation networks.

Recently, Forró's lab developed just such a solution. They created a water purifier, described in the Nature partner journal Clean Water, that is powered by a resource nearly all of the world’s most vulnerable people have access to: the sun.

Surprise from the quantum world

The ferromagnetism of the topological isolator manganese-bismuth-telluride only arises when the atomic structure fails. To do this, some manganese atoms (green) must be moved out of their original position (second green atomic plane from above). Only when there are manganese atoms in all levels with bismuth atoms (gray) is the magnetic orientation of the manganese atoms so contagious that ferromagnetism arises.
Illustration Credit: Jörg Bandmann / ct.qmat

The Würzburg-Dresden Cluster of Excellence ct.qmat has designed a ferromagnetic topological isolator - a milestone on the way to energy-efficient quantum technologies.

As early as 2019, an international research team around the material chemist Anna Isaeva - then junior professor at the Würzburg-Dresden Cluster of Excellence ct.qmat - complexity and topology in quantum materials - succeeded in producing the first antiferromagnetic topological isolator manganese-bismuth-tilluride. (Mn2Te4) a little sensation.

This miracle material no longer needs a strong external magnetic field - it brings its own inner magnetic field with it. This offers the opportunity for new types of electronic components that magnetically encode information and transport it on the surface without resistance. This could make information technology more sustainable and energy-saving in the future, for example. Since then, researchers worldwide have been analyzing different facets of this promising quantum material.

Researchers create exotic quantum light states

The graphic symbolizes how photons are coupled after they have been scattered on an artificial atom - a so-called quantum dot - in a cavity resonator.
Illustration Credit: © University of Basel

Coupled light particles could advance both medical imaging and quantum computing.

Light particles, also called photons, do not normally interact with each other. An international research team has now been able to show for the first time that a few photons can be manipulated in a controlled manner and brought into interaction. This opens up new opportunities in the development of quantum technologies. The results are described by a team from the University of Basel, the University of Sydney and the Ruhr University Bochum in the journal Nature Physics, published online on the 20th. March 2023.

Measure distances and transmit information using light

Photons do not interact with each other in a vacuum; they can fly through each other undisturbed. This makes them valuable for data transfer because information can be transported almost trouble-free at the speed of light. Light is helpful not only for data transmission, but also in certain measuring instruments, because it can be used to determine tiny distances, for example in medical imaging. The sensitivity of such measuring instruments depends on the average number of photons in the system.

Ultrafast beam-steering breakthrough at Sandia Labs

As a red beam of light is reflected in an arch, Prasad Iyer, right, and Igal Brener demonstrate optical hardware used for beam steering experiments at Sandia National Laboratories’ Center for Integrated Nanotechnologies.
Photo Credit: Craig Fritz

In a major breakthrough in the fields of nanophotonics and ultrafast optics, a Sandia National Laboratories research team has demonstrated the ability to dynamically steer light pulses from conventional, so-called incoherent light sources.

This ability to control light using a semiconductor device could allow low-power, relatively inexpensive sources like LEDs or flashlight bulbs to replace more powerful laser beams in new technologies such as holograms, remote sensing, self-driving cars and high-speed communication.

“What we’ve done is show that steering a beam of incoherent light can be done,” said Prasad Iyer, Sandia scientist and lead author of the research, which was reported in the current issue of the journal Nature Photonics. 

Incoherent light is emitted by many common sources, such as an old-fashioned incandescent light bulb or an LED bulb. This light is called incoherent since the photons are emitted with different wavelengths and in a random fashion. A beam of light from a laser, however, does not spread and diffuse because the photons have the same frequency and phase and is thus called coherent light.

Sculpting quantum materials for the electronics of the future

Artistic view. Curvature of the space fabric due to the superposition of spin and orbital states at the interface between lanthanum aluminate (LaAlO3) and strontium titanate (SrTiO3).
Illustration Credit: © Xavier Ravinet – UNIGE

An international team led by the UNIGE has developed a quantum material in which the fabric of space inhabited by electrons can be curved on-demand.

The development of new information and communication technologies poses new challenges to scientists and industry. Designing new quantum materials - whose exceptional properties stem from quantum physics - is the most promising way to meet these challenges. An international team led by the University of Geneva (UNIGE) and including researchers from the universities of Salerno, Utrecht and Delft, has designed a material in which the dynamics of electrons can be controlled by curving the fabric of space in which they evolve. These properties are of interest for next-generation electronic devices, including the optoelectronics of the future. These results can be found in the journal Nature Materials.

The telecommunications of the future will require new, extremely powerful electronic devices. These must be capable of processing electromagnetic signals at unprecedented speeds, in the picosecond range, i.e. one thousandth of a billionth of a second. This is unthinkable with current semiconductor materials, such as silicon, which is widely used in the electronic components of our telephones, computers and game consoles. To achieve this, scientists and industry are focusing on the design of new quantum materials.

First detection of neutrinos made at a particle collider

The FASER (Forward Search Experiment) detector in the tunnel of CERN’s Large Hadron Collider (LHC) in Geneva.
Photo Credit: © 2021-2023 CERN

Neutrinos are fundamental particles that played an important role in the early phase of the universe. They are key to learning more about the fundamental laws of nature, including how particles acquire mass and why there is more matter than antimatter. Despite being among the most abundant particles in the universe they are very difficult to detect because they pass through matter with almost no interaction. They are therefore often called “ghost particles”.

Neutrinos have been known for several decades and were very important for establishing the standard model of particle physics. But most neutrinos studied by physicists so far have been low-energy neutrinos. Previously, no neutrino produced at a particle collider had ever been detected by an experiment. Now, an international team including researchers from the Laboratory for High Energy Physics (LHEP) of the University of Bern has succeeded in doing just that. Using the FASER particle detector at CERN in Geneva, the team was able to detect very high energy neutrinos produced by brand a new source: CERN’s Large Hadron Collider (LHC). The international FASER collaboration announced this result on March 19 at the MORIOND EW conference in La Thuile, Italy.

‘Terminator zones’ on distant planets could harbor life

Some exoplanets have one side permanently facing their star while the other side is in perpetual darkness. The ring-shaped border between these permanent day and night regions is called a “terminator zone.” In a new paper in The Astrophysical Journal, physics and astronomy researchers at UC Irvine say this area has the potential to support extraterrestrial life.
Illustration Credit: Ana Lobo / University of California, Irvine

In a new study, University of California, Irvine astronomers describe how extraterrestrial life has the potential to exist on distant exoplanets inside a special area called the “terminator zone,” which is a ring on planets that have one side that always faces its star and one side that is always dark.

“These planets have a permanent day side and a permanent night side,” said Ana Lobo, a postdoctoral researcher in the UCI Department of Physics & Astronomy who led the new work, which was just published in The Astrophysical Journal. Lobo added that such planets are particularly common because they exist around stars that make up about 70 percent of the stars seen in the night sky – so-called M-dwarf stars, which are relatively dimmer than our sun.

The terminator is the dividing line between the day and night sides of the planet. Terminator zones could exist in that “just right” temperature zone between too hot and too cold.

“You want a planet that’s in the sweet spot of just the right temperature for having liquid water,” said Lobo, because liquid water, as far as scientists know, is an essential ingredient for life.

On the dark sides of terminator planets, perpetual night would yield plummeting temperatures that could cause any water to be frozen in ice. The side of the planet always facing its star could be too hot for water to remain in the open for long.

New kind of transistor could shrink communications devices on smartphones

Electrical & Computer Engineering research scientist Ding Wang and graduate student Minming He from Prof. Zetian Mi’s group, University of Michigan, are working on the epitaxy and fabrication of high electron mobility transistors (HEMTs) based on a new nitride material, ScAlN, which has been demonstrated recently as a promising high-k and ferroelectric gate dielectric that can foster new functionalities and boost device performances.”
Photo Credit: Marcin Szczepanski/Lead Multimedia Storyteller, Michigan Engineering

Integrating a new ferroelectric semiconductor, it paves the way for single amplifiers that can do the work of multiple conventional amplifiers, among other possibilities

One month after announcing a ferroelectric semiconductor at the nanoscale thinness required for modern computing components, a team at the University of Michigan has demonstrated a reconfigurable transistor using that material.

The study is a featured article in Applied Physics Letters.

“By realizing this new type of transistor, it opens up the possibility for integrating multifunctional devices, such as reconfigurable transistors, filters and resonators, on the same platform—all while operating at very high frequency and high power,” said Zetian Mi, U-M professor of electrical and computer engineering who led the research, “That’s a game changer for many applications.”