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Category: particle physics

Neutrons Illuminate the Magnetic Dance of Chiral Phonons

Neutron scattering has provided a new and broader view of the twirling collective atomic vibrations in a magnetic crystal.

Phonons—quantized conveyors of sound and heat in solids—are usually visualized as collective vibrations in which atoms simply bounce back and forth, almost as if they were weights on springs. However, atoms can sometimes form “chiral phonons” that twirl and swivel clockwise or counterclockwise, in a way that resembles a coordinated dance [1]. When these circular, chiral motions entrain ionic charge, they generate a magnetic moment, which suggests that there might be a way to control sound and heat using magnetic fields. Until recently, this magnetic dance was primarily observed using optical techniques, granting access to only one corner of the “stage”—the point in the phonon’s momentum space where the momentum is nearly zero. Song Bao of Nanjing University in China and his collaborators have now broadened the view of momentum space by using inelastic neutron spectroscopy.

Superfluids emerge in 2D moiré crystal formed from time, study predicts

Conventional crystals are materials in which atoms arrange themselves in repeating spatial patterns. Time crystals, on the other hand, are phases of matter characterized by repeating motions over time without constantly heating up, breaking a physical rule known as time-translation symmetry.

Researchers at East China Normal University and Shanghai Jiao Tong University recently predicted the formation of a new type of time crystal, dubbed a two-dimensional (2D) moiré time crystal. This crystal was theorized to emerge when periodic perturbations (i.e., regular, repeated disturbances) are applied to ultracold atoms held in a smooth, continuous trap, as opposed to an optical lattice trap. The paper is published in the journal Physical Review Letters.

“We were inspired by two exciting concepts in physics,” Keye Zhang, professor at East China Normal University and co-senior author of the paper, told Phys.org. “The first is the concept of ‘twistronics,’ where twisting atom-thin layers creates moiré patterns with exotic material properties. While the second is that of ‘time crystals’ (a new phase of matter with persistent rhythmic motion). We wondered: could we combine these ideas by treating time itself as a dimension that can be ‘twisted’?”

Physicists discover long-predicted ‘clock magnetism’ in an atomically thin crystal

Strange things happen to materials when you peel them down, layer by layer, from thick chunks all the way to sheets just an atom thick. Reporting in the journal Nature Materials, a team led by physicists at The University of Texas at Austin has experimentally demonstrated a sequence of exotic magnetic phases in an ultrathin material that fully realizes, for the first time, a theoretical model of two-dimensional magnetism first proposed in the 1970s. The researchers say the advance might inspire new ultracompact technologies.

The sequence of exotic magnetic phases involves two key transitions that occur as certain materials cool down towards absolute zero. Both transitions have been observed experimentally on their own before, but never together in a complete sequence.

When the researchers cooled an atomically thin sheet of nickel phosphorus trisulfide (NiPS3) to temperatures between −150 and −130° C, the material entered the first special magnetic phase, called a Berezinskii–Kosterlitz–Thouless (BKT) phase. In this regime, the magnetic orientations associated with individual atoms in the material—known as magnetic moments—form swirling patterns called vortices. Pairs of these vortices wind in opposite directions, one clockwise and the other counterclockwise, and remain tightly bound together.

Catching light in air: Programmable Mie voids boost light matter interaction

Atomically thin semiconductors such as tungsten disulfide (WS2) are promising materials for future photonic technologies. Despite being only a single layer of atoms thick, they host tightly bound excitons—pairs of electrons and holes that interact strongly with light—and can efficiently generate new colors of light through nonlinear optical processes such as second-harmonic generation.

These properties make them attractive for quantum optics, sensing, and on-chip light sources. At the same time, their extreme thinness imposes a basic limitation: There is very little material for light to interact with. As a result, emission and frequency conversion are often weak unless the surrounding photonic environment is carefully engineered.

A study published in Advanced Photonics introduces a new way to address this challenge by reshaping not the two-dimensional material itself, but the space beneath it. The researchers demonstrate a hybrid platform in which a monolayer of WS2 is placed on top of nanoscale air cavities, known as Mie voids, carved into a high-index crystal of bismuth telluride (Bi2Te3). The work shows that these voids can strongly enhance light emission and nonlinear optical signals, while also allowing direct visualization of localized optical modes.

Heavier hydrogen makes silicon T centers shine brighter for quantum networks

Quantum technologies, computers or other devices that operate leveraging quantum mechanical effects, rely on the precise control of light and matter. Over the past decades, quantum physicists and material scientists have been trying to identify systems that can reliably generate photons (i.e., light particles) and could thus be used to create quantum technologies.

One approach for generating photons relies on silicon color centers, such as the emerging T center. Color centers are defects or irregularities in the crystal structure of silicon characterized by a different arrangement of atoms.

The T center and other silicon color centers can emit light in the wavelength band that is already used by fiber-optic internet cables, which is desirable for the development of quantum networks and quantum communication systems.

Why Reality Is Just Information | Leonard Susskind

Have you ever felt like the world around you isn’t exactly… “real”? Modern physics is starting to suggest something incredible: The universe isn’t made of atoms, energy, or particles. It is made of Information. In this video, we explore the radical “It from Bit” theory and the Holographic Principle. From the mysterious paradoxes of Black Holes and Hawking Radiation to the way quantum entanglement might actually create the fabric of space and time, we dive deep into the mind-bending reality of quantum mechanics. In this video, we cover: Why Stephen Hawking conceded the Black Hole Information Paradox. The Ryu-Takayanagi formula: How entanglement builds geometry. Why 3D space might just be a 2D holographic projection. The “It from Bit” philosophy by John Wheeler. How consciousness relates to Integrated Information Theory (IIT). If reality is just a pattern of qubits in a vast Hilbert space, what does that make us? Join us as we deconstruct the material world and look at the “source code” of the universe. #QuantumPhysics #HolographicUniverse #ItFromBit #TheoreticalPhysics #ScienceDocumentary #SpaceTime #quantuminformation

Structures of hantavirus glycoprotein tetramers

This surface protein complex for the Andes virus is a mushroom-shaped structure called a Gn-Gc tetramer. To map the 3D structures, the team first produced virus-like particles that mimic a real virus, but without the genome that makes a virus infectious. They then used a cryo-electron microscope—which shines an electron beam through a frozen sample and detects the shadows created by molecules—to reconstruct the three-dimensional structures of the Gn-Gc tetramers on the surface of the virus-like particles.

But there was a twist: To obtain extremely high-resolution structures, the researchers painstakingly identified and isolated shadows from only the tetramers that were pointing sidewise relative to the electron beam and ignored those pointing in other directions. This allowed them to borrow a reconstruction method typically used on individual proteins.

The resulting structures have an extremely high resolution of 2.3 angstroms, meaning details the size of just a couple of atoms were effectively captured. That’s enough to represent a transformational improvement over another team’s model of the tetramer from a few years ago, at a resolution of 12 angstroms, still tiny but large enough to produce some key inaccuracies – ones effectively corrected with the newer method and resulting structure.

These latest structures show the Gn-Gc tetramer in a particular state before it has infected a cell. For vaccines or antibody therapies to be most effective against a hantavirus, mimicking surface proteins at this pre-infection stage is essential. ScienceMission sciencenewshighlights.

Hantaviruses, transmitted from rodents to people, have a death rate approaching 40%. They’re found around the world, and because there are no approved vaccines or treatments, they’re among the pathogens of highest concern for future pandemics. They made news in the United States last year when Betsy Arakawa, the wife of actor Gene Hackman, died from a hantavirus infection in New Mexico in March.

New findings published in the journal Cell about the Andes virus, a hantavirus endemic to the southwestern U.S. and other parts of North and South America, represent a crucial first step towards much-needed vaccines and antibody therapies for this and other hantaviruses.

Continue reading “Structures of hantavirus glycoprotein tetramers” | >

How close are we to true AI?

Understanding consciousness is the ultimate prize for creators of artificial intelligence. Nevertheless, consciousness theory will also shape how we view ourselves and our place in the world. Although AI systems can mimic human reasoning, they can only regurgitate the input data. They are sophisticated pattern recognizers and content remixers, but cannot step beyond the limitations of the input. Understanding consciousness would enable us to transition from synthetic to synthesis, unlocking unlimited potential.

Computer scientists hope that recurrent computation will somehow ‘awaken’ code to consciousness. Yet the spectacular achievements of large language and diffusion models have not moved beyond imitation. We train models on the outputs of consciousness—our language, our art, our logic—while remaining entirely ignorant of the process that produces them. An AI can write a gut-wrenching paragraph about sadness by replicating patterns, vocabulary, and syntax. But it knows nothing of grief. It can create a shadow play, yet knows nothing of the object that casts it. This imitation, while impressive, should not be mistaken for a proper understanding of consciousness. No amount of coloring can turn the shadow into a solid object.

To reverse-engineer the mind, we need a blueprint. The pressing need to advance AI is a physicalist theory of consciousness, the architecture of subjective experience itself. The Fermionic Mind Hypothesis (FMH) is such a physicalist framework. It posits that selfhood is structurally and functionally analogous to a fermion in physics. The self’s persistent core operates as an energy-regulating system, maintaining mental equilibrium through continuous thermodynamic cycles. Within this cycle, cognitive processes such as decision-making are wave-particle transitions that capture the inherent nondeterminism and contextual collapse of probabilistic mental states.

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