A new theory linking atomic disorder to heat flow offers a strong foundation for predicting thermal conductivity in materials ranging from crystals to amorphous carbon.
Category: materials
Hydrogen’s role in generating free electrons in silicon finally explained
Researchers announced that they have achieved the world’s first elucidation of how hydrogen produces free electrons through the interaction with certain defects in silicon. The achievement has the potential to improve how insulated gate bipolar transistors (IGBTs) are designed and manufactured, making them more efficient and reducing their power loss. It is also expected to open up possibilities for future devices using ultra-wide bandgap (UWBG) materials.
In the global drive toward carbon neutrality, efforts to make power electronics more efficient and energy-saving are accelerating worldwide. IGBTs are key components responsible for power conversion, so improving their efficiency is a major priority. While hydrogen ion implantation has been used for about half a century to control electron concentration in silicon, the underlying mechanism has remained unclear until now.
In 2023, Mitsubishi Electric and University of Tsukuba jointly discovered a defect complex in silicon that contributes to increasing electron concentration. They confirmed that this complex is formed when an interstitial silicon pair and hydrogen bind, but the reason why free electrons are newly generated in this process was still unclear.
Chiral phonons create orbital current via their own magnetism
In a new study, an international group of researchers has found that chiral phonons can create orbital current without needing magnetic elements—in part because chiral phonons have their own magnetic moments. Additionally, this effect can be achieved in common crystal materials. The work has potential for the development of less expensive, energy-efficient orbitronic devices for use in a wide array of electronics.
All electronic devices are based upon the charge of an electron, and electrons have three intrinsic properties: spin, charge and orbital angular momentum. While researchers have long explored the use of spin as a more efficient way to create current, the field of orbitronics —based upon using an electron’s orbital angular momentum, rather than its spin, to create a current flow—is still relatively new.
“Traditionally it has been technically challenging to generate orbital current,” says Dali Sun, co-corresponding author on the study published in Nature Physics. Sun is a professor of physics and member of the Organic and Carbon Electronics Lab (ORaCEL) at North Carolina State University.
‘Smart’ crystals self-repair at —320°F, could unlock new space tech
The team, led by NUY Abu Dhabi’s Panče Naumov, developed a material they dubbed smart molecular crystals. In a paper published in the journal Nature Materials, they outlined the observation process that allowed them to identify the material’s impressive properties.
During experiments, they observed that the material could be mechanically damaged in extreme cold and then repair itself. Importantly, it also recovered its ability to transmit light after being damaged. This is essential for low-temperature flexible optical and electronic devices.
According to a press statement, the material can restore its structure even at temperatures as low as −196°C (−320°F), the boiling temperature of liquid nitrogen. The material also remains functional throughout a wide temperature range, going up to 150°C (302°F).
Metamaterial Performs Computations in a New Way
A research team has developed a triangular mechanical network that can squeeze and wiggle in a multitude of preprogrammed ways [1]. The metamaterial design—realized in experiments with various materials, including Legos—may have applications from shock absorption to protein modeling. But the researchers also demonstrated that their structures can solve problems in matrix algebra. Performing computations in materials without converting information to electrical signals could be useful when durability and energy efficiency are more important than computing power, for example, in components of some soft robots.
Recent work showed that a mechanical system can perform similar computations [2]. However, this previous demonstration was limited in the number of inputs and outputs that it could accommodate, says Yair Shokef of Tel Aviv University in Israel. It also had rather large components that made it difficult to adapt to different applications.
Shokef and his colleagues, who produced the latest demonstration, built their 2D networks from equilateral triangles. Each triangle consisted of rigid beams with hinge points at each vertex and at the center of each side, for a total of three so-called corner nodes and three edge nodes per triangle. Importantly, each triangle had one or two “bonds”—beams that connected edge nodes and that determined the ways in which the triangle could be distorted or flexed.
Transforming hydrogen energy by flattening granular catalysts into paper-thin sheets
Catalysts are the invisible engines of hydrogen energy, governing both hydrogen production and electricity generation. Conventional catalysts are typically fabricated in granular particle form, which is easy to synthesize but suffers from inefficient use of precious metals and limited durability.
KAIST researchers have introduced a paper-thin sheet architecture in place of granules, demonstrating that a structural innovation—rather than new materials—can simultaneously reduce precious-metal usage while enhancing both hydrogen production and fuel-cell performance.
Professor EunAe Cho of the Department of Materials Science and Engineering has developed a new catalyst architecture that dramatically reduces the amount of expensive precious metals required while simultaneously improving hydrogen production and fuel-cell performance.
Using magnetic frustration to probe new quantum possibilities
Research in the lab of UC Santa Barbara materials professor Stephen Wilson is focused on understanding the fundamental physics behind unusual states of matter and developing materials that can host the kinds of properties needed for quantum functionalities.
In a paper published in Nature Materials, Wilson’s lab group has reported on an innovative way to use a phenomenon referred to as frustration of long-range order in a material system to engineer unconventional magnetic states with potential relevance for quantum technologies.
At the same time, Wilson emphasized, “This is fundamental science aimed at addressing a basic question. It’s meant to probe what physics may be possible for future devices.”
