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Category: materials – Page 56

Wafer lens changes X-ray beam size by more than 3,400 times

Using only a single-crystal piezoelectric thin wafer of lithium niobate (LN) instead of the usual two-part structure, a group from Nagoya University in Japan has created a deformable mirror that changes X-ray beam size by more than 3,400 times. This improved tuning range enhances both imaging and analysis, especially for the X-rays used in industry.

Their technique is based on LN, a material that has piezoelectricity, meaning that it changes its surface shape in response to voltage. Traditional X-ray mirrors are rigid and resistant to being deformed, making it difficult to adapt them to changing experimental conditions in real time, but the new technique can significantly change size, making it useful for a range of situations encountered in industry.

The study is published in the journal Scientific Reports.

Stronger Magnetic Fields Without Superconductors? Scientists Say Yes

Two German physicists have unveiled a compact magnet layout that outperforms the famed Halbach array, delivering stronger, more even magnetic fields without bulky superconductors.

Their 3D-printed ring stacks matched analytic predictions and could slash the cost of MRI machines while opening doors for levitation tech and particle accelerators.

Breakthrough in Magnetic Field Generation.

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.

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