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Category: materials

To study the interactions between electrons in a material, physicists have come up with a number of tricks over the years. These interactions are interesting, among other things, because they lead to technologically important phenomena such as superconductivity.

In most materials, however, are very weak and, therefore, hard to detect. One of the tricks that researchers have used for a while now consists in reducing the motional energy of the electrons by artificially creating a with a large lattice constant—that is, with a large distance between the lattice sites in the crystal. In this way, the interaction energy, which is still small, becomes relatively more important, so that interaction effects become visible.

However, the so-called moiré materials used for this suffer from the disadvantage that inside them it is not only the motion of electrons that is modified with respect to ordinary crystal lattices, but also other physical processes that are needed for studying the material.

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Composite adhesives like epoxy resins are excellent tools for joining and filling materials including wood, metal, and concrete. But there’s one problem: once a composite sets, it’s there forever. Now there’s a better way. Researchers have developed a simple polymer that serves as a strong and stable filler that can later be dissolved. It works like a tangled ball of yarn that, when pulled, unravels into separate fibers.

A new study led by researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) outlines a way to engineer pseudo-bonds in materials. Instead of forming chemical bonds, which is what makes epoxies and other composites so tough, the chains of molecules entangle in a way that is fully reversible. The research is published in the journal Advanced Materials.

“This is a brand new way of solidifying materials. We opened a new path to composites that doesn’t go with the traditional ways,” said Ting Xu, a faculty senior scientist at Berkeley Lab and one of the lead authors for the study.

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Researchers at the Fritz Haber Institute have developed the Automatic Process Explorer (APE), an approach that enhances our understanding of atomic and molecular processes. By dynamically refining simulations, APE has uncovered unexpected complexities in the oxidation of palladium (Pd) surfaces, offering new insights into catalyst behavior. The study is published in the journal Physical Review Letters.

Kinetic Monte Carlo (kMC) simulations are essential for studying the long-term evolution of atomic and molecular processes. They are widely used in fields like surface catalysis, where reactions on material surfaces are crucial for developing efficient catalysts that accelerate reactions in and pollution control. Traditional kMC simulations rely on predefined inputs, which can limit their ability to capture complex atomic movements. This is where the Automatic Process Explorer (APE) comes in.

Developed by the Theory Department at the Fritz Haber Institute, APE overcomes biases in traditional kMC simulations by dynamically updating the list of processes based on the system’s current state. This approach encourages exploration of new structures, promoting diversity and efficiency in structural exploration. APE separates process exploration from kMC simulations, using fuzzy machine-learning classification to identify distinct atomic environments. This allows for a broader exploration of potential atomic movements.

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A team of scientists has just landed a massive grant to build materials strong enough to withstand the blistering heat and radiation inside a fusion reactor, where temperatures soar beyond 180 million degrees Fahrenheit (100 million degrees Celsius).

The U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E) allocated USD 2.3 million to the University of Kentucky to lead the development of next-generation materials that could make commercial fusion power a reality.

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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.

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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.

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