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Long-range magnetic interactions govern how a ferrimagnet approaches its phase transition

Close to a phase transition, very different materials can follow the same mathematical rules. The concept of universality, which groups seemingly distinct systems based on their common properties, was developed to describe this phenomenon.

In magnetic systems, ferromagnets, ferrimagnets and antiferromagnets fall into the same universality class when short-range interactions dominate and their spatial and spin dimensionalities coincide. However, this universality has not been established when long-range interactions dominate.

In insulating magnets, long-range coupling may originate from dipole-dipole interactions. However, dipolar-driven mean-field criticality has only been firmly established in ferromagnets, leaving the ferrimagnetic and antiferromagnetic cases unexplored.

Krypton gas emerges as a new ingredient for quantum computing

To commercialize quantum computing, manufacturers need high-quality superconducting materials for microchips, but they also require a reliable, sustainable nanofabrication process. Tantalum is a corrosion-resistant metal that meets the first criterion but not the second. That’s because it has to be deposited on a substrate at temperatures that typically exceed 400°C (752°F)—too hot for many semiconductor foundries’ current tools.

Cornell researchers have developed a method that uses krypton gas to slash that deposition temperature to 200°C (392°F) while depositing tantalum on silicon, a standard high-quality substrate. The process resulted in thin films that also have substantially higher electronic conductivity.

“Tantalum as a material has been shown to be very exciting from a device performance perspective, but its manufacturability had some question marks because of integration challenges such as required process temperatures,” said Valla Fatemi, assistant professor and Aref and Manon Lahham Faculty Fellow in the Cornell Duffield College of Engineering, who led the project.

Largest catalog yet of how human cells read DNA shows how chemical marks alter genetic instructions

Every cell in the body contains essentially the same DNA, yet a brain cell behaves differently from a muscle cell or an immune cell. The difference lies largely in how each cell reads its genetic instructions.

Proteins called transcription factors bind specific DNA sequences and help control when and where genes are active. They direct processes ranging from embryonic development to immune function. When this regulation goes wrong, disease can result. But although the human genome contains around 1,600 transcription factors, the DNA-binding preferences of many have remained unknown.

An international collaboration led by Timothy Hughes at the University of Toronto has now filled many of these gaps in a study published in Nature. The researchers combined five experimental platforms with computational analyses, performing more than 4,800 experiments and identifying DNA-binding motifs for 177 transcription factors that were previously poorly characterized. The work added around 130 distinct motifs to the known vocabulary of human gene regulation.

Unusual superconductivity could emerge in valley-imbalanced rhombohedral graphene

Superconductors are materials in which electrical current flows with a resistance of zero, typically below specific temperatures. In conventional superconductors, this state of matter emerges when two electrons bind together at low temperatures, forming so-called Cooper pairs.

Yet some materials, referred to as unconventional superconductors, exhibit superconductivity under unusual conditions and cannot be explained by conventional theories. Understanding these unusual cases could lead to the development of superconductors that can operate at high enough temperatures to be used in real-world devices with less refrigeration.

Researchers at Harvard University and the University of Stuttgart theoretically demonstrated that an unusual form of graphene, known as valley-imbalanced rhombohedral tetralayer graphene, could host unconventional superconducting states.

A new approach to building noise-resistant quantum sensors

Quantum sensors, devices that collect measurements by exploiting quantum-mechanical phenomena, could potentially detect extremely weak magnetic, gravitational and electromagnetic signals with greater sensitivity than classical sensors. Some quantum sensors leverage entanglement, a phenomenon that prompts distant particles to become so strongly linked that the physical state of one particle dictates the state of the others.

Despite their potential, these sensors are often very sensitive to noise (i.e., external disturbances originating from the surrounding environment). This means that even small environmental disturbances and hardware imperfections can disrupt delicate quantum states and reduce the devices’ sensing precision.

Researchers at the Quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area, Southern University of Science and Technology and Shenzhen University recently introduced a new method to develop noise-adaptive sensors that can collect more precise measurements. Their approach, outlined in a paper published in Physical Review Letters, relies on a variational quantum circuit, a sequence of quantum operations that can be adjusted to search for a state that performs well on specific measurement tasks.

New photonic crystal method improves single-photon sources for quantum networks

Quantum communication promises many advantages over today’s standard technologies, including absolutely secure transmission of large amounts of data. However, it requires single photons—and generating them is very difficult. Researchers at the Technical University of Munich (TUM) and the Munich Center for Quantum Science and Technology (MCQST) have developed a new method that overcomes the problems of previous approaches.

Instead of amplifying the desired frequency, the researchers selectively suppress unwanted frequencies. Until now, so-called resonators have mostly been used to produce single photons—tiny optical structures that influence photon sources, causing them to emit light predominantly at a specific frequency. However, these resonators function only within a narrow frequency range and must be precisely tuned to the respective photon source.

Researchers at TUM and MCQST have developed a new approach that takes the opposite route. Instead of causing emitters to emit more light at a specific frequency, they adapt the emitter’s environment so that less light is emitted at unwanted frequencies.

Scientists ‘see’ nanoscale forces, providing evidence of electric fields at the air‑water interface

Bubbles are round, and we know surface tension does that. But squeeze that gas-liquid boundary into a space only a few tens of nanometers wide—could other forces be at work?

Now, an international team from Kyushu University, Nankai University, Stanford University and the University of Alberta has taken a direct look. Publishing on July 14 in the Journal of the American Chemical Society, they combined three-dimensional transmission electron microscopy (3D TEM) with force analysis to provide evidence for a powerful electric field at nanoconfined air-water interfaces.

“Water looks simple, but it’s actually incredibly complex,” says Qin-Yi Li, associate professor at Kyushu University’s Faculty of Engineering. “Its structure is especially rich at the water-air interface, and it shifts dramatically with scale.”

Curved surfaces reshape active materials, localizing vibrations near defects

Many materials, both living and engineered, are powered from within. Scientists have thoroughly investigated how such ‘active’ materials operate, but so far, mostly in circumstances where the curvature of the environment does not play a role. In research published in Physical Review Letters this week, a team of physicists proposes a framework to describe how active materials operate in the presence of curvature. The framework explains striking biological observations and may lead to geometry as a design parameter for new materials.

Examples of active materials include tissues made of moving cells and mechanical metamaterials that use embedded motors or actuators. A major difference between such active materials and ordinary materials lies in the way they deform. Push an ordinary material, and it will deform where the force acts. Active materials, on the other hand, can generate further forces that redirect deformations, leading to all kinds of unexpected, but often quite useful, behavior.

A striking example comes from observations in biological experiments, where starfish embryos were found to self-organize into crystal-like structures on a water surface. In this example, an extra factor comes into play: The water surface in the test tubes used in the experiments is not flat but slightly curved—just like the surface of water in an ordinary drinking glass that curves upward where the water touches the glass. One consequence of the curvature is that the starfish embryos don’t fit on the surface in a completely regular pattern: Instead, the pattern has occasional irregularities or defects.

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