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Physicists take Hall effect in a new direction Carnegie Mellon University scientists have uncovered a new phenomenon that challenges a longstanding assumption about how electronic materials respond to magnetic fields. The discovery broadens the fundamental understanding of the Hall effect, a principle widely used to measure the magnetic and electronic properties of materials. Published in Nature Materials, the research could lay the groundwork for simpler, more versatile magnetic sensing technologies used in electronics, transportation and medical imaging. The Hall effect has been a key tool for studying material properties for more than a century. In 1879, Edwin Hall showed that applying a magnetic field perpendicular to a material deflects moving charges, producing a measurable voltage. By analyzing this signal, scientists can determine whether electric current is carried by negative or positive charges, how many of those charges are moving through the material and how easily they flow. Today, the Hall effect is integral to widely used sensing technologies found in systems ranging from automobiles to computer keyboards. In the latest work, researchers in Carnegie Mellon's Department of Physics, working in the Lab for Investigating Quantum Materials, Interfaces and Devices (LIQUID), identified a new form of the Hall effect. "For a long time, people thought the Hall effect only worked when the magnetic field was applied perpendicular to the plane of the film. We've shown that that's not true—you can also get a response when the field is in-plane," said Simranjeet Singh, an associate professor of physics. The discovery expands the role of the Hall effect as a core tool in physics because it allows for a magnetization-dependent Hall response in more than one direction. This allows researchers to probe and understand multidimensional magnetic and topological configurations in condensed matter systems. "Beyond fundamental importance, this discovery can enable novel planar device architectures and sensor types, such as vector magnetometry, by measuring the out-of-plane and in-plane anomalous Hall effect signals in the same device," Singh said. From theory to reality The idea of an in-plane anomalous Hall effect was proposed theoretically but never experimentally demonstrated—until now. "People proposed it and ideas were out there, but it's very difficult to make a magnetic material with the right symmetry to do it," Singh said. "What we did was we found a material with the right symmetry and we made it magnetic." Source: Phys.org @EverythingScience

Tiny mirror that controls light in 3D could make microscopes smaller and faster Researchers use tightly focused laser beams to image biological samples, shape materials with microscopic precision and generate displays. But using those beams in three dimensions requires more than sweeping light from side to side, as the light must also rapidly refocus at different depths. That often requires separate optical components, one to steer the light and another to change where it comes into focus. Penn State researchers have developed a state-of-the-art tiny mirror that can do both at record speeds, potentially slimming down and speeding up future optical systems used in brain imaging, augmented reality goggles and precision manufacturing. "Being able to quickly control light in three dimensions with a single device offers a significant improvement in the overall size and weight of an optical system," said Hunter Shillingburg, doctoral student in electrical engineering and first author of the study published in Microsystems & Nanoengineering. A neuroscience use case For Shillingburg, one potential application stands out: neuroscience. "Although the fields are all strongly related, I see the most potential being in neurobiology," he said. "The system could lead to smaller, mountable miniature microscopes for studying neurobiology in active subjects as well as lighter glasses and headsets for augmented reality." Neurons, the tightly packed nerve cells that send and receive signals in the brain, can become active in just thousandths of a second. Studying that activity requires fast-acting and precise tools. A small device that rapidly directs a focused beam of light to different spots and depths could eventually help miniature microscopes study brain activity in moving subjects or examine very small regions of the brain. Faster scanning could have another benefit in biological imaging, Shillingburg said. Sensitive samples can be damaged or fade when exposed to too much light, so reducing exposure time can help researchers image living cells and other biological materials while limiting those effects. Source: Phys.org @EverythingScience

Scientists Intrigued by a Surprising Result in the Search for Dark Matter Dark matter is the invisible stuff that accounts for roughly 85% of the mass in the universe, and for decades, physicists have been trying to figure out what it's made of. Now an experimental facility located nearly a mile below ground in South Dakota has recorded a single interaction between subatomic particles that doesn't match what's expected from normal matter. Has a dark-matter particle been detected at last? It's too early to say, but the anomaly is definitely attracting attention from dark-matter detectives. The detection was made at the Sanford Underground Research Facility, or SURF, a converted gold mine that now houses the world's most sensitive detector for dark matter. Since 2021, the LUX-ZEPLIN Dark Matter Experiment has been recording flashes of light in a shielded tank that's filled with 10 tons of ultra-pure liquid xenon. Those flashes occur when weakly interacting massive particles, or WIMPs, collide with xenon atoms. The results are analyzed by an international team of 250 scientists and engineers from 39 institutions. Researchers recently reviewed 220 days' worth of data collected by the detector between March 2023 and April 2024. An earlier analysis searched for faint signals from the simplest kinds of WIMP interactions, but the follow-up review widened the search parameters to look for more energetic interactions. One event exhibited a spectrum of nuclear recoil energy that was difficult to explain in the context of known background signals involving normal matter. "We’re very intrigued to see this event in the data, in the region where we expect dark matter to show up and the competing backgrounds are very low,” Rick Gaitskell, a professor at Brown University and the spokesperson for LUX-ZEPLIN, said in a news release. “With only one event, we don’t want to get ahead of ourselves. We are not claiming to have seen dark matter. But we have seen something interesting that we want to share with the scientific community for their input.” A report on the research was presented this week in a scientific talk at the 2026 TeV Particle Astrophysics conference in Japan. The report will be submitted to Physical Review Letters for peer-reviewed publication. The research team's analysis determined that the particle behind the anomalous event would have more than 200 times the mass of a proton — if it was truly a piece of dark matter. But it's too early to make that assumption. The significance level for the detection was 2.6 sigma, which is well below the 5-sigma standard for claiming a discovery. For now, the statistics suggest there's a roughly 0.5% chance that the event could be explained by known background interactions... Source: Universe Today @EverythingScience