Photoemission electron microscopy (PEEM) experiments have demonstrated that the circulation direction of a magnetic vortex can be switched by the application of an electric field, opening the door to digital devices with more streamlined system designs, improved performance, and greater energy efficiency. ... Read more »
The Mystery of the Lightweight Electrons
Copper oxides are important for superconductivity applications but are difficult to understand due to complex charge, spin, and orbital interactions. Now, studies at the ALS have found such a system in which observations of effective electron mass are at odds with state-of-the-art electronic-structure calculations. ... Read more »
Hybrid LED Phosphors Combine Performance and Durability
Light-emitting diodes (LEDs) last a long time and are very energy efficient. However, white LEDs currently rely on phosphor materials doped with rare-earth elements (REEs) that are increasingly costly and in short supply. A new class of hybrid phosphor materials shows promise as REE-free alternatives. ... Read more »
The Ancient Roman Secret to Concrete Resilience in Seawater
Researchers used x-ray microdiffraction to trace the complex sequences of crystal growth in concrete from ancient Roman pier and breakwater sites. The results indicate that minerals continue to form over millennia as seawater percolates through, reinforcing the cementing matrix in a kind of regenerative process. ... Read more »
A Multifunctional Material with Electric-Field Control
Three distinct crystalline phases with different electronic, magnetic, and optical properties were reversibly induced in a material through the insertion and extraction of ions by an electric field at room temperature. Such multifunctional materials are desirable for many applications, from smart windows to spintronics.
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New Studies of Ancient Concrete Could Teach Us to Do as the Romans Did
A new look inside 2,000-year-old concrete—made from volcanic ash, lime (the product of baked limestone), and seawater—has provided new clues to the evolving chemistry and mineral cements that allow ancient harbor structures to withstand the test of time. ... Read more »
2D Material’s Traits Could Send Electronics R&D Spinning in New Directions
Working at the ALS, researchers have found another family of materials where they can both explore the physics of 2D topological insulators and do experiments that may lead to future applications. The material—known as 1T’-WTe2—bridges two flourishing fields of research: that of so-called 2D materials and topological materials. ... Read more »
Fine-Tuning Oxygen Vacancies with Coherent Strain
Researchers have demonstrated a novel way to systematically strain-engineer oxygen vacancies in complex transition-metal oxide thin films. The work advances our ability to tailor such defects, small changes in which can lead to dramatic changes in material properties such as conductivity and magnetism. ... Read more »
Strain Turns Tin into a 3D Topological Dirac Semimetal
A small amount of compressive strain turns a nonmetallic form of tin into a 3D topological Dirac semimetal—a kind of “supermetal” with very high electron mobility. With its rich topological phase diagram, the material shows promise for both novel physics and eventual device applications. ... Read more »
Modulating Infrared Light with 2D Black Phosphorus
Two-dimensional materials represent a promising new frontier in the field of optoelectronics. Most progress so far, however, has been in the visible-light range. Now, at the ALS, researchers have measured the infrared transmission spectra of ultrathin samples of black phosphorus under an applied electric field. ... Read more »
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