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Category: particle physics – Page 48

Chirality refers to objects that cannot be superimposed onto their mirror images through any combination of rotations or translations, much like the distinct left and right hands of a human. In chiral crystals, the spatial arrangement of atoms confers a specific “handedness,” which—for example—influences their optical and electrical properties.

A Hamburg-Oxford team has focused on so-called antiferro-chirals, a type of non-chiral crystal reminiscent of antiferro-magnetic materials, in which anti-align in a staggered pattern leading to a vanishing net magnetization. An antiferro-chiral crystal is composed of equivalent amounts of left-and right-handed substructures in a unit cell, rendering it overall non-chiral.

The research team, led by Andrea Cavalleri of the Max-Planck-Institut for the Structure and Dynamics of Matter, used light to lift this balance in the non-chiral material boron phosphate (BPO4), in this way inducing finite chirality on an ultrafast time scale.

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Perovskite solar cells are attracting attention as next-generation solar cells. These cells have high efficiency, are flexible, and can be printed, among other features. However, lead was initially used in their manufacture, and its toxicity has become an environmental issue.

Therefore, a method for replacing lead with tin, which has a low environmental impact, has been proposed. Nevertheless, tin is easily oxidized; consequently, the efficiency and durability of tin are lower than those of lead perovskite solar cells.

To improve the durability of tin perovskite by suppressing tin oxidation, a method that introduces large organic cations into tin perovskite crystals to form a two-dimensional layered structure called Ruddlesden-Popper (RP) tin-based perovskites has been proposed. However, the internal state of this structure and the mechanism by which it improves performance have not been fully elucidated.

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The chemical composition of a material alone sometimes reveals little about its properties. The decisive factor is often the arrangement of the molecules in the atomic lattice structure or on the surface of the material. Materials science utilizes this factor to create certain properties by applying individual atoms and molecules to surfaces with the aid of high-performance microscopes. This is still extremely time-consuming and the constructed nanostructures are comparatively simple.

Using , a research group at TU Graz now wants to take the construction of nanostructures to a new level. Their paper is published in the journal Computer Physics Communications.

“We want to develop a self-learning AI system that positions individual molecules quickly, specifically and in the right orientation, and all this completely autonomously,” says Oliver Hofmann from the Institute of Solid State Physics, who heads the research group. This should make it possible to build highly complex molecular structures, including logic circuits in the nanometer range.

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In a groundbreaking study published in Nature, researchers from the University of British Columbia, the University of Washington, and Johns Hopkins University have identified a new class of quantum states in a specially engineered graphene structure. They found topological electronic crystals in twisted bilayer–tilayer graphene, made by stacking and twisting two-dimensional graphene layers.

Graphene, composed of carbon atoms arranged in a honeycomb structure, has unique electrical properties due to the way electrons hop between the carbon atoms.

Prof. Joshua Folk from UBC explains that stacking two graphene flakes with a slight twist creates a geometric interference effect known as a moiré pattern, changing how electrons move, slowing them down, and twisting their motion.

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Quantum entanglement—a phenomenon where particles are mysteriously linked no matter how far apart they are—presents a long-standing challenge in the physical world, particularly in understanding its behavior within complex quantum systems.

A research team from the Department of Physics at The University of Hong Kong (HKU) and their collaborators have recently developed a novel algorithm in quantum physics known as ‘entanglement microscopy’ that enables visualization and mapping of this extraordinary phenomenon at a microscopic scale.

By zooming in on the intricate interactions of entangled particles, one can uncover the hidden structures of quantum matter, revealing insights that could transform technology and deepen the understanding of the universe.

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The Search for Quantum Gravity

Physics faces a profound crisis as it struggles to unify two foundational theories: general relativity and quantum mechanics. While general relativity explains gravity and large-scale phenomena, quantum mechanics governs the microscopic world of particles. Despite their individual successes, these theories conflict, prompting the need for a unified framework known as quantum gravity.

One promising approach is string theory, which posits that particles are actually vibrating strings in up to 11 dimensions. However, its lack of testable predictions has spurred alternative ideas, such as loop quantum gravity. This theory envisions space and time as a network of minuscule loops, challenging the notion of time as a fundamental construct. Remarkably, loop quantum gravity suggests time might not exist at all.

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Researchers from the University of British Columbia, the University of Washington, and Johns Hopkins University have identified a new class of quantum states in a custom-engineered graphene structure.

Published in Nature, the study reports the discovery of topological electronic crystals in twisted bilayer–trilayer graphene, a system created by introducing a precise rotational twist between stacked two-dimensional materials.

“The starting point for this work is two flakes of graphene, which are made up of carbon atoms arranged in a honeycomb structure. The way electrons hop between the carbon atoms determines the electrical properties of the graphene, which ends up being superficially similar to more common conductors like copper,” said Prof. Joshua Folk, a member of UBC’s Physics and Astronomy Department and the Blusson Quantum Matter Institute (UBC Blusson QMI).

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The story of collapsing stars is often said to go from neutron stars directly to black holes, but there could be a number of intermediate steps where the structure of matter becomes one of quark soup. In this talk we take a look at the theory and the possibly evidence for such Quark stars — and compare them with the most dangerousmaterial thought possible — the strangelet.

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A new study that provides unprecedented insights into the chemical bonding of antimony could have a profound impact on materials research. The collaboration between scientists from Leipzig University, RWTH Aachen University and the DESY synchrotron in Hamburg combined experimental measurements with theoretical calculations.

The findings will help scientists to better understand phase change materials and, in particular, improve their application in and thermoelectrics. The research has now been published in Advanced Materials.

The study combined experimental measurements with , with the aim of analyzing the nature and strength of the chemical bonding in antimony. “The strength of a bond depends directly on the distance between the atoms,” says Professor Claudia S. Schnohr of the Felix Bloch Institute for Solid State Physics at Leipzig University, adding that comparisons with other materials such as metals and semiconductors show that this distance dependence is characteristic of the type of chemical bond.

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