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Category: materials

Coupled electrons and phonons may flow like water in 2D semiconductors

A condition long considered to be unfavorable to electrical conduction in semiconductor materials may actually be beneficial in 2D semiconductors, according to new findings by UC Santa Barbara researchers published in the journal Physical Review Letters.

Electron-phonon interactions—collisions between charge-carrying electrons and heat-carrying vibrations in the atomic lattice of the material—are considered the primary cause of electrons slowing down as they travel through semiconductor material. But according to UCSB mechanical engineers Bolin Liao and Yujie Quan, when electrons and phonons are considered as a single system, these interactions in atomically thin material prove to actually conserve total and energy, and could have important implications for 2D semiconductor design.

“This is in sharp contrast to three-dimensional systems where you have a lot of momentum loss processes,” said Liao, who specializes in thermal and energy science.

Topological Twist for Phase Transitions

Contrary to conventional wisdom, so-called order parameters that distinguish symmetry-governed phases of matter can have topological structure.

From materials developing magnetization patterns to metals becoming superconductors, a wide range of phase transitions can be qualitatively described by a single framework known as Ginzburg-Landau theory [1, 2]. This framework generally assumes that a key quantity in its descriptions, called an order parameter, has trivial topology. But now, Canon Sun and Joseph Maciejko at the University of Alberta, Canada, have shown that order parameters can have hidden topological structure [3]. The researchers have developed an extension to Ginzburg-Landau theory that incorporates such hidden topology, revealing features absent from the original framework.

Symmetry constitutes a fundamental concept in physics. It appears in many guises but is especially important when studying how interactions of countless microscopic constituents give rise to macroscopic order in condensed-matter systems. For example, below a critical temperature, an ordinary magnet has a net magnetization because its spins all align in the same direction, breaking rotational symmetry. If the magnet is heated above that temperature, it loses its magnetization as its spins point in random directions, restoring rotational symmetry.

More pathways that previously thought can lead to optical topological insulators

The candidate pool for engineered materials that can help enable tomorrow’s cutting-edge optical technologies—such as lasers, detectors and imaging devices—is much deeper than previously believed.

That’s according to new research from the University of Michigan that examined a class of materials known as topological insulators. These materials have exciting and tunable properties when it comes to how they transmit energy and information.

“We see this as a step toward building a more versatile and powerful foundation for future photonic technologies,” said Xin Xie, a research fellow in the U-M Department of Physics and lead author of the recent study in the journal Physical Review X.

A new atomistic route to viscosity—even near the glass transition

We rarely think about how liquids flow—why honey is thick, water is thin or how molten plastic moves through machines. But for scientists and engineers, understanding and predicting the viscosity of materials, especially polymers, is essential.

Viscosity governs how substances deform and flow under stress, which in turn affects how they are processed, how they behave in industrial pipelines, in environmental settings, or in consumer products, and how they respond to changing temperatures.

Traditionally, to calculate the of a liquid or polymer melt based on molecular simulations on computers, people rely on a method called the Green–Kubo formalism. It works by tracking how internal stresses fluctuate and decay over time inside a simulated material at thermodynamic equilibrium.

High explosives in slow motion: Freezing molecules in place shows chemical reactions

Safe and effective high explosives are critical to Lawrence Livermore National Laboratory’s (LLNL) mission of stockpile stewardship. It is relatively simple to study the composition of such material before a detonation or examine the soot-like remnants afterward. But the chemistry in between, which dictates much of the detonation process, evades experimental interrogation as it passes by in a few nanoseconds or less.

In a study published in the Proceedings of the National Academy of Sciences, researchers from SLAC National Accelerator Laboratory and LLNL triggered a slow decomposition of a high explosive and measured the effects on the molecules within it. The work provides the proof of concept for a process that could be extended to examine ultra-fast dynamic chemistry during detonations and illuminates intermediate structures that have never been experimentally seen before.

At the Stanford Synchrotron Radiation Lightsource, the team used X-rays to both trigger the involved in decomposition and measure the results.

“Like Nothing Ever Seen Before”: Astronomers Discover a Colossal Milky Way Cloud Containing the Mass of 160,000 Suns

IN A NUTSHELL 🌌 Astronomers discovered a colossal molecular cloud named M4.7–0.8 in the Milky Way, weighing as much as 160,000 suns. 🔭 The Green Bank Telescope was instrumental in identifying this cloud located 23,000 light-years away, revealing its pivotal role in material transport. ⭐ Giant Molecular Clouds (GMCs) like M4.7–0.8 are critical for understanding

MIT’s New 3D Chips Could Make Electronics Faster and More Energy-Efficient

The low-cost, scalable technology enables seamless integration of high-speed gallium nitride transistors onto a standard silicon chip. Gallium nitride is an advanced semiconductor material that is expected to play a key role in the next generation of high-speed communication systems and the power

Overcoming Long-Held Limitations: Korean Scientists Unveil Next-Generation Energy Storage Technology

Developing next-generation energy storage technologies that can deliver both high power and high capacity at the same time. A research team led by Dr. Bon-Cheol Ku and Dr. Seo Gyun Kim from the Carbon Composite Materials Research Center at the Korea Institute of Science and Technology (KIST), alo

Zoning out could be beneficial—and may actually help us learn faster

Aimlessly wandering around a city or exploring the new mall may seem unproductive, but new research from HHMI’s Janelia Research Campus suggests it could play an important role in how our brains learn.

By simultaneously recording the activity of tens of thousands of neurons, a team of scientists from the Pachitariu and Stringer labs discovered that learning may occur even when there are no specific tasks or goals involved.

Published in Nature, the new research finds that as animals explore their environment, neurons in the visual cortex—the brain area responsible for processing —encode visual features to build an internal model of the world. This information can speed up learning when a more concrete task arises.