Scientists discovered that glass molecules shift unpredictably, reversing time at a microscopic level. This challenges our understanding of time and material science.
Category: materials – Page 20
A research team led by Prof. Wang Xianlong and Dr. Wang Pei from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has discovered a concurrent negative photoconductivity (NPC) and superconductivity in PbSe0.5 Te0.5 by pressure-induced structure transition. The study has been published in Advanced Materials.
NPC is a unique phenomenon where the conductivity of a material decreases due to the trapping of charge carriers in localized states, leading to a reduction in the number of free carriers, which is contrary to the more common behavior of positive photoconductivity (PPC).
Though NPC holds great promise in next-generation semiconductor optoelectronics and its application potential has recently reached far beyond photodetection, the phenomenon has rarely been reported. In particular, concurrent NPC and superconductivity are rarely observed at high-pressure due to the lack of in situ experimental measuring facilities.
Why do avalanches start to slide? And what happens inside the “pile of snow?” If you ask yourself these questions, you are very close to a physical problem. This phenomenon not only occurs on mountain peaks and in snow masses, where it is rather uncontrolled—it is also studied in the laboratory at the microscopic level in materials with a disordered particle structure, for example in glasses, granular materials or foams.
Particles can “slide” in a similar way to avalanches, causing the structure to lose its stability and become deformable, even independently of a change in temperature. But what happens inside such a shaky structure?
Physicist Matthias Fuchs from the University of Konstanz and his colleagues Florian Vogel and Philipp Baumgärtel are researching these disordered solids. Two years ago, they solved an old puzzle about glass vibrations by revisiting a forgotten theory. “Now we have continued the project to answer the question of when an ‘irregular house of cards collapses.’ We want to find out when an amorphous solid loses its stability and starts to slide like a pile of sand,” says Fuchs.
Researchers in Germany have developed a special technique that will allow better control over atomic reflections in quantum sensors. This new approach uses carefully engineered light pulses as atomic mirrors to cut noise and sharpen quantum measurements.
There’s a big difference between regular and quantum sensors. The former relies on classical physics to measure properties like temperature, pressure, or motion. However, their measurements are affected by factors like thermal noise, material quality, and environmental disturbances.
Buildings cost a lot these days. But when concrete buildings are being constructed, there’s another material that can make them less expensive: mud.
MIT researchers have developed a method to use lightly treated mud, including soil from a building site, as the “formwork” molds into which concrete is poured. The technique deploys 3D printing and can replace the more costly method of building elaborate wood formworks for concrete construction.
“What we’ve demonstrated is that we can essentially take the ground we’re standing on, or waste soil from a construction site, and transform it into accurate, highly complex, and flexible formwork for customized concrete structures,” says Sandy Curth, a PhD student in MIT’s Department of Architecture who has helped spearhead the project.
Most metals expand as their temperature rises. The Eiffel Tower, for example, stands about 10 to 15 centimeters taller in summer than in winter due to thermal expansion. However, this effect is highly undesirable for many technical applications. As a result, researchers have long sought materials that maintain a constant length regardless of temperature. One such material is Invar, an iron-nickel alloy known for its extremely low thermal expansion. The physical explanation for this property, however, remained unclear until recently.
Now, a collaboration between theoretical researchers at the Vienna University of Technology (TU Wien) and experimentalists at the University of Science and Technology Beijing has led to a significant breakthrough. Using complex computer simulations, they have unraveled the invar effect in detail and developed a so-called pyrochlore magnet—an alloy with even better thermal expansion properties than Invar. Over an exceptionally wide temperature range of more than 400 Kelvins, its length changes by only about one ten-thousandth of one percent per Kelvin.
Scientists have measured the quantum state of electrons for the first time, unlocking new insights into quantum mechanics and material science.
Dr. Ben Allardyce and Ph.D. candidate Mr. Martin Zaki from Deakin’s Institute for Frontier Materials (IFM) have delivered a world first in next-generation materials research. Silkworm silk is a protein-based fiber with mechanical properties rivaling petroleum-derived synthetic fibers, yet spun using a fraction of the energy. Despite decades of research, aspects of natural silkworm spinning remain a mystery.
Published in Advanced Materials, the IFM discovery takes researchers one step closer to solving this mystery by wet-spinning a new class of silk that produces fibers that outperform natural silk.
This research, led by Dr. Allardyce and Mr. Zaki, with expert input from Sheffield University’s Professor Chris Holland, involves sidestepping degumming—a commonplace industrial process—and experimenting with dissolving whole silk fibers.
A research group recently discovered the disappearance of nonreciprocal second harmonic generation (SHG) in MnPSe₃ when integrated into a two-dimensional (2D) antiferromagnetic MnPSe₃/graphene heterojunction.
The research, published in Nano Letters, highlights the role of interfacial magnon-plasmon coupling in this phenomenon.
2D van der Waals magnetic/non-magnetic heterojunctions hold significant promise for spintronic devices. Achieving these functionalities hinges on the interfacial proximity effect, a critical factor. However, detecting the proximity effect in 2D antiferromagnetic/non-magnetic heterojunctions presents considerable challenges, due to the small size and weak signals associated with these structures.