Flat bands harbor exotic electron physics. A new way of realizing them could make the physics more accessible.
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Steering electrons with extreme ultraviolet light—team achieves quantum coherent control
Light is one of the most powerful tools scientists have for probing matter. By interacting with electrons, light reveals how atoms, molecules and materials are structured and how they evolve in time. Highly energetic ultraviolet and X-ray photons are particularly attractive because they can access electrons located close to atomic nuclei, where each chemical element carries its own distinctive electronic fingerprint.
While researchers can control electrons with visible and infrared lasers, extending these techniques to the XUV and X-ray domains has proven far more challenging. The international research team has now brought a new tool to that demanding region of the spectrum.
Custom frame timing captures ultrafast events across five orders of magnitude in time
Most conventional methods of ultrafast photography use evenly spaced intervals in which images are taken, but new developments have shown how much can be left out of the story, especially when multiple timescales are involved.
Ultrafast events, such as a laser pulse or shock-wave emission, can be captured using ultrafast imaging. Conventional methods of imaging operate on microsecond (millionths of a second) or millisecond (thousandths of a second) timescales and usually have a set, evenly spaced—or mostly evenly spaced—interval in which images are taken. While this can work to capture some characteristics of the ultrafast event, not every important and observable dynamic happens at neatly spaced intervals.
Quantum probability can’t be derived without assuming it first
For nearly a century, physicists have relied on the Born rule to calculate the chances of different outcomes when they measure a quantum system. Yet despite decades of effort, nobody has managed to derive the rule from more basic mathematical principles without making assumptions about probability along the way.
Through new analysis published in Physical Review A, Jiaxuan Zhang at the University of Oxford has shown that five of the most prominent derivations of the Born rule all depend on one such assumption. Her work suggests that quantum probabilities can’t simply be extracted from a theory that contains none to begin with.
Oxygen collisions show evidence of jet quenching, a signature of early-universe matter
New results from the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) provide strong evidence that smashing oxygen nuclei together at nearly the speed of light generates a quark-gluon plasma (QGP), a type of matter that existed just after the birth of the universe. The data, just published in Physical Review Letters, show that energetic jets of particles lose energy as they traverse the hot, dense matter left in the collision’s wake.
This energy loss phenomenon, known as jet quenching, has been one of the “smoking gun” signatures of QGP formation in collisions of larger atomic nuclei at RHIC, a U.S. Department of Energy (DOE) Office of Science user facility that operated at DOE’s Brookhaven National Laboratory from 2000 until earlier this year. This signature has also been observed in oxygen–oxygen collisions at the Large Hadron Collider (LHC), located at CERN, the European Particle Physics Laboratory. The analysis from RHIC at significantly lower collision energy sets a new lower boundary for the conditions capable of producing the primordial QGP in this small collision system.
“The QGP is believed to be the form of matter that filled the early universe—before the protons and neutrons that make up today’s atoms formed. Understanding its properties is essential for uncovering how the early universe evolved in its first microseconds,” said Li Yi, a professor of physics at Shandong University who oversaw the STAR analysis. “One of the most powerful ways scientists study the QGP is by identifying where its signatures appear—and just as importantly, where these signatures turn off,” she said.
A hidden rivalry between two quantum states at the heart of superconductors
Transmitting electricity without losing any energy may sound impossible, yet this is precisely the promise of superconductivity. For nearly 40 years, scientists have been working to understand materials that exhibit this remarkable property at relatively high temperatures. Unlocking their secrets could one day help make power grids more efficient, enhance medical technologies and support the development of quantum computing.
Among the most promising of these materials are cuprates, a family of copper-based compounds discovered in 1986. The breakthrough was so significant that its discoverers, Bednorz and Müller, were awarded the Nobel Prize in Physics the following year. Despite decades of research, however, the mechanisms that allow cuprates to become superconducting remain poorly understood.
At the heart of this puzzle lies the pseudogap, a mysterious quantum state whose exact role continues to spark debate. Some scientists believe it helps superconductivity emerge, while others see it as a competing phenomenon.
Soybean waste yields 3D-printable material that could help repair skin
Transforming a soybean processing byproduct into a material for skin protection and repair is the prospect outlined by a study that used okara, a residue from the production of tofu and soy-based beverages, to obtain a bioactive, biodegradable, 3D-printable biomaterial.
The material could contribute, in the future, to the development of devices for the local treatment of pain associated with breastfeeding and postoperative recovery following breast cancer surgery.
The interdisciplinary research was coordinated by Carmen Lammi, professor at the Department of Pharmaceutical Sciences of the University of Milan, in collaboration with the team led by professor Serena Graziosi of the Department of Mechanical Engineering at Politecnico di Milano, and with Raffaele Pugliese, a researcher at the NeMO Lab Research Center—Niguarda Hospital in Milan.
AI challenges math by solving the unsolvable
Announcements over recent months that artificial intelligence models have cracked previously unsolvable problems are shaking top-level mathematicians to the core, and they are now asking themselves: Where do we come in?
“All the avenues of research I had are now gone; we’re facing a new day,” Hugo Duminil-Copin, winner of the 2022 Fields Medal, one of the highest honors in mathematics, recently told his colleagues at the French Mathematical Society.
Since April, AI firms have regularly been publishing solutions to previously unsolved mathematical problems as they seek to demonstrate the power of their latest models.
Using eyedrops in space—wearable patch offers a new approach
Applying eyedrops is difficult in space, where there is almost no gravity. A KAIST research team has developed a wearable patch that delivers eyedrops to the eye without relying on gravity. The research team was led by Professor Ki-Hun Jeong from the Department of Bio and Brain Engineering, in collaboration with a research team led by Professor Se Joon Woo from Seoul National University Bundang Hospital. The paper is published in the journal Sensors and Actuators B: Chemical.
During long-duration space exploration, technologies that allow astronauts to manage their health without direct help from medical staff are essential. In particular, microgravity causes body fluids to shift toward the head, which can change the structure of the eyes and visual function. However, the standard method of applying eyedrops on Earth depends on drops falling by gravity, so it cannot be used in space without modification.
AI slays the dragon as four agents conquer Minecraft without human intervention
Minecraft is one of the world’s most popular video games, where players explore, gather resources, craft items and try to survive in a virtual universe constructed of 3D cubes that represent different materials.
The Ender Dragon is the game’s difficult final test. To reach and defeat this dragon, players must complete a long series of connected challenges, such as gathering raw resources, building tools and finding a hidden underground stronghold.
Now, four AI agents have done it, and they only needed one game-specific instruction: “defeat the Ender Dragon.”