Chemists identify a single molecule that naturally tiles in nonrepeating patterns, which could help build materials with novel electronic properties.
Category: materials – Page 30
A Versatile Design for a Metasurface Cavity
Periodic structures known as metamaterials can interact with electromagnetic waves in unusual ways. In one counterintuitive example, standing waves remain trapped in a volume even though they’re surrounded by radiating waves that should carry their energy away. These standing waves, called bound states in the continuum (BICs), can provide a boost to resonant systems—such as lasers, filters, or sensors—by mitigating radiative losses. Researchers have recently demonstrated a promising design that produces high-quality BICs; however, it works only at microwave frequencies. Simulations by Pietro Brugnolo and his colleagues at the Technical University of Denmark now suggest that a straightforward change could allow the design to be adapted to optical wavelengths [1].
The previous design involves thin metamaterials, or metasurfaces, made of metallic bars arranged around cylindrical cavities. In such a configuration, BICs emerge when characteristic metasurface resonances match the cavity resonance. The metallic elements, however, result in resistive losses when used at wavelengths shorter than those of microwaves. Brugnolo’s team thus set out to investigate an all-dielectric version of the scheme.
The researchers simulated devices in which the metallic elements were replaced with silicon particles distributed on a cylindric surface. Their results showed that the structure displayed both an electrical and an effective magnetic response, which could be tailored to create the standing-wave patterns characteristic of BICs. For a wave at telecommunication wavelengths (1550 nm), their simulations predicted a cavity quality factor of 1.7 × 104, on par with the microwave version of the same scheme.
X-Ray Spectral Imaging Probes How Sun-Like Plasma Blocks Light
Temporal measurements in conditions similar to those in the Sun rebut a leading hypothesis for why models and experiments disagree on how much light iron absorbs.
Understanding how light interacts with matter inside stars is crucial for predicting stars’ evolution, structure, and energy output. A key factor in this process is opacity—the degree to which a material absorbs radiation. Recent experimental findings have challenged long-standing models, showing that iron, a major contributor to stellar opacity, absorbs more light than expected. This discrepancy has profound implications for our understanding of the Sun and of other stars. Over the past two decades, three groundbreaking studies [1–3] have taken major steps toward resolving this mystery, using advanced laboratory experiments to measure iron’s opacity under extreme conditions similar to those of the Sun’s interior. However, the discrepancy remained, with researchers hypothesizing that it came from systematic errors from temporal gradients in plasma properties.
Light has been transformed into a ‘supersolid’ for the first time
Supersolids are strange materials that behave like both a solid and a fluid due to quantum effects – and now researchers have created an intriguing new type of supersolid from laser light.
Human Skin Can Taste Things, And Scientists Just Figured Out Why
Ever set off too many of the bitter taste receptors on your tongue? You probably spat out whatever it was in your mouth, and that’s our best guess for why we even have them: to stop us from ingesting things that might be harmful.
Our skin cells have the same receptors, which serve a similar purpose on a cellular level: to detect bitter substances. New research led by Okayama University of Science biologists builds on our knowledge of the type-2 taste receptors (TAS2Rs) found in the skin’s keratinocytes, finding their role is also to keep potentially harmful materials from sticking around and causing damage.
Once thought to be confined to the tongue, TAS2Rs are actually spread much further throughout the body. They line your colon, your stomach, and your upper airways.
Researchers discover magnetic equivalent of the Lyddane-Sachs-Teller relation
Materials are known to interact with electromagnetic fields in different ways, which reflect their structures and underlying properties. The Lyddane-Sachs-Teller relation is a physics construct that describes the relationship between a material’s static and dynamic dielectric constant (i.e., values indicating a system’s behavior in the presence or absence of an external electric field, respectively) and the vibrational modes of the material’s crystal lattice (i.e., resonance frequencies).
This construct, first introduced by physicists Lyddanne, Sachs and Teller in 1941, has since been widely used to conduct solid-state physics research and materials science studies. Ultimately, it has helped better explain and delineate the properties of various materials, which were then used to create new electronic devices.
Researchers at Lund University recently extended the Lyddane-Sachs-Teller relation to magnetism, showing that a similar relation links a material’s static permeability (i.e., its non-oscillatory response to a magnetic field) to the frequencies at which it exhibits a magnetic resonance. Their paper, published in Physical Review Letters, opens new exciting possibilities for the study of magnetic materials.
Deep Inside Earth, Two Giant Mantle Structures Rewrite Geological History
Researchers have typically assumed that both LLVPs are similar to each other in nature, e.g. chemical composition and age, because seismic waves travel through them in similar ways. But a new study, co-authored by Dr. Paula Koelemeijer (Department of Earth Sciences, University of Oxford), has challenged this view by modelling the formation of the LLVPs through time.
By combining a model of mantle convection, including a reconstruction of how tectonic plates have moved over the Earth’s surface over the last billion years, the study has been able to show that the African LLVP consists of older and better mixed material than the Pacific LLVP, which contains 50% more and younger subducted oceanic crust (and therefore is more different to the surrounding mantle). The resulting differences in density could also explain why the African LLVP is more diffuse and taller than its Pacific counterpart.
