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Category: materials

How Elasticity Shapes Nematic Criticality

A 19th-century theory of elasticity inspires a new way to analyze a quantum phase transition that has become central to modern quantum materials research.

When a crystalline metal enters a so-called nematic state, the onset of strong fluctuations among interacting electrons spontaneously breaks the crystal’s rotational symmetry and distorts both the physical lattice and the notional Fermi surface. This transition, known as nematic criticality, has been observed near the onset of superconductivity in cuprates, pnictides, and twisted bilayer graphene and could hold the key to explaining these poorly understood forms of superconductivity. Now Joe Meese and Rafael Fernandes of the University of Illinois-Champaign have proposed that nematic criticality is more selective in how it breaks rotational symmetry than previously assumed [1, 2]. The selectivity arises not from a novel microscopic mechanism but from a geometric constraint.

Nematic order typically develops spontaneously upon cooling; hydrostatic pressure can shift the transition, while uniaxial stress can tune the transition or induce nematicity by linearly coupling to lattice strain. Because of this connection, nematic order obeys the same mechanical laws as other continuous lattice deformations do. Consequently, as Meese and Fernandes showed, nematic order splits into two classes. One class is compatible with the lattice and can turn critical; the other is incompatible with the lattice and is therefore suppressed (Fig. 1). In the conventional picture, the energy cost of completing a nematic transition is “softened”—that is, reduced by the emergence of fluctuations as the transition is approached. That condition remains true in Meese and Fernandes’ picture, but the softening is not spread over all the possible distortions allowed by symmetry. Rather, elasticity itself selects the modes that participate in nematic criticality.

There’s a range of magic angles to study superconductivity in a twisted 2D semiconductor

Last year, tungsten diselenide (WSe2) had its magic moment. Two independent research groups discovered “magic angles” at which two atom-thin layers of the unique semiconductor, when twisted relative to one another into what’s known as a moire pattern, can superconduct electricity. Cory Dean and his colleagues at Columbia documented superconductivity at a 5° twist angle; upstate at Cornell, Jie Shan and Kin Fai Mak’s team saw it at around 3.5°. Until then, graphene was the only other moire material capable of the feat.

Writing again in Nature on April 1, Dean and his colleagues fill in what happens between their observed magic angle and Cornell’s. Though the initial results struck researchers as two potentially distinct types of superconductivity, they are in fact smoothly connected. “Graphene has a magic angle of 1.1°. WSe2 has a magic continuum,” said Columbia physics graduate student Yinjie Guo, lead author of both Columbia Nature papers.

That wide continuum of superconducting twist angles makes WSe2 a more robust platform to explore the phenomenon than graphene, which cannot deviate by more than a tenth of a degree from its magic angle. “That’s a very specific condition you have to get to, and it’s been a real bottleneck,” noted Dean. “Working with WSe2 is extremely reproducible, which makes it much more possible to build new theories about superconductivity.”

Surprising link between metallicity and superconductivity uncovered in twisted trilayer graphene

Superconductivity is a state of matter characterized by an electrical resistance of zero, typically at very low temperatures. Past studies have found that in various materials, this unique state is accompanied by unusual electron arrangements.

In some superconductors, for instance, electrons spontaneously align in a preferred direction, breaking a property known as rotational symmetry. This directional arrangement of electrons is also known as electronic nematicity.

Moreover, some superconductors also exhibit a strange metallicity. This is a phase characterized by unusual changes in a material’s electrical resistance, which cannot be explained by standard physical theories.

A truly invisible device that does not disturb its surroundings and its metamaterial shell

Metamaterials are carefully engineered materials that possess desirable properties and can be used to manipulate electromagnetic, acoustic, or other types of waves in interesting ways. Some materials scientists and engineers have been trying to use these materials to develop so-called invisible devices, or, in other words, devices that do not disturb the environment around them or reveal their presence to other technologies nearby.

Most proposed approaches for realizing invisible devices entail surrounding devices with a metamaterial shell that prevents scattering. While devices created using these strategies do not disturb their surrounding environment, they still distort what is happening within the metamaterial shell, thus they remain partly visible.

Researchers at Fudan University have introduced a new approach to realize devices that are truly and entirely invisible using metamaterials. Their proposed solution, outlined in a paper published in Physical Review Letters, was found to eliminate scattering effects both outside and inside a metamaterial cloaking shell.

NASA Plans to Test Fire on The Moon Ahead of Future Missions

There’s one particular challenge facing the crewed missions of the near future that scares mission planners more than almost any other: fire.

A new paper from researchers at NASA’s Glenn Research Center and Johnson Space Center and Case Western Reserve University details a planned mission to test the flammability of materials on the Moon’s surface – where they expect flame to act much differently than it does here on Earth.

On Earth, gravity causes hot gases to rise, drawing fresh, cool oxygen to the base of the flame. In some cases where the material is marginally flammable, this can result in a phenomenon called “blowoff”, which actually extinguishes the fire.

Targeting biomolecular condensates: beyond dissolution

Biomolecular condensates control key cellular processes, from gene expression to signal transduction, by organizing molecules through selective compartmentalization. Increasing evidence links their dysregulation to cancer, neurodegeneration, and other diseases, positioning condensates as promising therapeutic targets. This review explores emerging strategies that go beyond dissolving pathological condensates, including approaches that induce, redirect, or reprogram their dynamics, composition, and physical state. Rather than inhibiting individual proteins, these interventions reshape the cellular organization itself. By targeting the material and functional properties of condensates, such strategies offer a new conceptual framework for therapeutic design in complex, dysregulated biological systems.

New Hydrogel Helps Bone Grow Without Transplant or Implants

A new hydrogel may offer a way to regenerate bone—without transplants or implants.

Early research shows the material can support bone growth by creating a scaffold that encourages the body’s own repair processes. It’s designed to integrate with tissue and break down as new bone forms.

While still in early stages, the approach could represent a shift toward less invasive, regenerative options for bone repair.

Researchers have developed a soft laser-printed scaffold made almost entirely of water that bone cells readily colonize.

A monster black hole appeared first, then its galaxy began to grow around it

Using observations gathered by the James Webb Space Telescope (JWST), an international team of astronomers have revealed that one supermassive black hole in the early universe must have formed before a galaxy developed around it. Publishing their results in Monthly Notices of the Royal Astronomical Society, a team led by Roberto Maiolino at the University of Cambridge hope their results could lead to a better understanding of the origins of these immense objects.

Supermassive black holes (SMBH) are known to lurk at the centers of most galaxies, including our own Milky Way. Carrying up to billions of times the mass of the sun, they have presented a long-standing conundrum to astronomers.

According to our latest models, black holes form from the remnants of supernova explosions, which most often occur when massive stars reach the ends of their lives. Afterwards, they can grow by consuming gas from surrounding accretion disks—but their growth rate is restricted by a brightness threshold called the “Eddington limit.” Beyond this point, the outward pressure from radiation exceeds the gravitational pull, and material is ejected into space.

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