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Category: materials

Why twisted bilayer graphene stops superconducting near high-dielectric substrates

Superconductors are materials that can conduct electricity with a resistance of zero. In so-called conventional superconductors, this occurs at low temperatures when electrons become bound into pairs, known as Cooper pairs.

In some other materials, however, superconductivity (SC) emerges via other electron pairing mechanisms that are still poorly understood. These materials, called unconventional superconductors, include twisted bilayer graphene (tBLG), a two-dimensional material created by stacking two single sheets of graphene on top of each other, one of which is rotated in relation to the other by a precise small angle.

One factor that plays a role in unconventional SC is the so-called dielectric constant. This is the measure of how well a material reduces the electric forces between charged particles.

Magnetic ‘super lenses’ open new window on high-temperature superconductors

An international research team, including scientists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), has achieved a methodological breakthrough in the study of superhydrides, a promising class of superconductors. For the first time, the team succeeded in analyzing lanthanum superhydrides under extreme pressure using nuclear magnetic resonance spectroscopy.

The research is published in the journal Advanced Science.

Superconductors are characterized by the fact that their electrical resistance vanishes below a material-specific critical temperature, allowing them to conduct electricity without loss. For most known materials, this transition temperature is below about 140 Kelvin (minus 133 degrees Celsius), which requires complex cooling technology for practical applications. Consequently, researchers are actively searching for materials that exhibit superconductivity at significantly higher temperatures.

Sound waves create mist that can act like ‘plant sunscreen’

RMIT University researchers have developed a new way to coat fragile surfaces, including living plant leaves, using high‑frequency sound waves to create a fine mist that can act like a plant sunscreen.

The approach tackles a long‑standing challenge in materials science: many promising coatings require high temperatures or harsh processing, making them unsuitable for delicate surfaces such as living tissue, soft plastics or emerging electronic materials.

The research paper, “Ambient one‑step synthesis and direct coating of highly crystalline covalent organic frameworks on arbitrary surfaces,” is published in Science Advances.

Quantum geometry applied to light-based systems expands toolkit for topological photonics

Quantum geometry describes quantum states in systems with changing system parameters, such as an electron spinning in a magnetic field whose direction is slowly changing. The state of the electron evolves, and this change is quantified by what is known as the quantum geometric distance.

With the help of this abstract geometric description, it is possible, for example, to explain superconductivity—defined as the resistance-free conduction of current—in exotic quantum materials. Another example can be found in quantum metrology: by applying quantum geometry, fundamental limits on measurement accuracy can be determined.

Scientists program materials just by spinning them

There is something universally appealing about the slap bracelet, and the way a simple tap causes it to switch between a straight shape and a curled one. What you probably didn’t know is that a slap bracelet’s satisfying snap is the same principle behind bistable structures. These can toggle between two stable positions (one representing 0 and the other 1) to store data directly within their physical forms as mechanical bits (m-bits).

Because of their exciting potential for efficient control of robotic and other mechanical systems, researchers have been engineering special materials with programmable structures (programmable metamaterials) for years. But until now, actual programming of such systems has been a major challenge: mechanical bits must typically be controlled individually, which is extremely cumbersome and time-consuming.

Now, researchers in the Flexible Structures Laboratory (fleXLab) in EPFL’s School of Engineering, the Dutch research institute AMOLF, and Leiden University have found a way to program metamaterials globally with a surprisingly simple solution: rotation. By tuning a spinning platform’s speed, direction, and acceleration, the researchers can harness forces arising in a rotating system—such as centrifugal and Euler forces—to make elastic beams snap back and forth, creating a simple new way to “write” multiple mechanical bits at once.

Inexpensive material compresses light, paving the way for photonic microcircuits in the terahertz range

A two-dimensional lamellar crystal composed of atomically thin layers of lead iodide (PbI2) could be used to manufacture a new generation of circuits that use light and mechanical vibrations (rather than electrons) to transmit information in the terahertz frequency range.

Researchers at the Brazilian Center for Research in Energy and Materials (CNPEM), in partnership with colleagues from the University of Lille (France) and other international institutions, have studied this technology and published their findings in Nature Communications.

The terahertz band corresponds to a low-energy region of the electromagnetic spectrum situated between infrared and microwaves. Despite this, it is considered crucial for developing high-speed communication technologies.

Elastic rules may explain why nematic crystals look ordered and disordered at once

Electronic nematicity is a phase of some crystalline solids in which electrons’ collective properties, such as charge or spin densities, organize themselves into ordered patterns, lowering the crystal’s rotational symmetry. This phase is found across a wide range of diverse materials, making nematicity crucial to understanding emergent solid-state phenomena, such as unconventional superconductivity and magnetism.

Lately, experimentalists have encountered a hurdle to understanding nematicity: despite exhibiting nematic order at macroscopic scales, at the microscopic level, many nematic materials seem to exhibit disorder instead.

To address this seeming paradox, theorists at the University of Illinois Urbana-Champaign have invented a new way of looking at the interactions between nematicity and elasticity, incorporating aspects of elasticity theory, whose impacts on nematicity have previously been overlooked.

Magnetic fields can ‘revive’ superconductivity in nickelates, research reveals

A research team led by Professor Denver Li Danfeng, Associate Dean (Research and Postgraduate Education) of the College of Science and Associate Professor in the Department of Physics at City University of Hong Kong (CityUHK), has achieved a significant advance in superconducting materials.

The team has discovered a magnetic-field-induced “re-entrant superconductivity” phenomenon in infinite-layer nickelate superconductors, in which superconductivity—initially suppressed by a magnetic field—reappears at higher field strengths. This finding challenges the conventional understanding that magnetic fields suppress superconductivity and opens up new directions for exploring unconventional superconducting mechanisms and next-generation superconducting materials.

The findings are published in Nature, titled “Field re-entrant superconductivity in Eu-doped infinite-layer nickelates.”

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