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Category: materials

Twisted trilayer graphene shows high kinetic inductance and quantum coherence

Superconductivity is an advantageous physical phenomenon observed in some materials, which entails an electrical resistance of zero below specific critical temperatures. This phenomenon is known to arise following the formation of so-called Cooper pairs (i.e., pairs of electrons).

There are two known types of superconductivity, known as conventional and unconventional superconductivity. In , the formation of Cooper pairs is mediated by the interaction between electrons and phonons (i.e., vibrations in a crystal’s lattice), as explained by Bardeen-Cooper-Schrieffer (BCS) theory.

Unconventional superconductors, on the other hand, are materials that exhibit a superconductivity that is not prompted by electron–phonon interactions. While many past studies have tried to shed light on the mechanisms underpinning unconventional superconductivity, its underlying physics remains poorly understood.

Magnetic frustration in atacamite triggers dramatic cooling when exposed to strong fields

Natural crystals fascinate with their vibrant colors, their nearly flawless appearance and their manifold symmetrical forms. But researchers are interested in them for quite different reasons: Among the countless minerals already known, they always discover some materials with unusual magnetic properties.

One of these is atacamite, which exhibits magnetocaloric behavior at low temperatures—that is, the material’s temperature changes significantly when it is subjected to a . A team headed by TU Braunschweig and the HZDR has now investigated this rare property. In the long term, the results, now published in Physical Review Letters, could help to develop new materials for energy-efficient magnetic cooling.

The emerald-green mineral atacamite, named for the place it was first found, the Atacama Desert in Chile, gets its characteristic coloring from the copper ions it contains. These ions also determine the material’s magnetic properties: they each have an unpaired electron whose spin gives the ion a —comparable to a tiny needle on a compass.

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.

Revolutionary “Material Maze” Could Prevent Bacterial Infections

Scientists used patterned plastic surfaces to trick bacteria into halting their own spread. These designs may prevent infections without the need for antimicrobial drugs. Scientists at the University of Nottingham have identified surface patterns that significantly reduce the ability of bacteria

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.