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Category: particle physics – Page 5

Magnetic materials have become indispensable to various technologies that support our modern society, such as data storage devices, electric motors, and magnetic sensors.

High-magnetization ferromagnets are especially important for the development of next-generation spintronics, sensors, and high-density data storage technologies. Among these materials, the iron-cobalt (Fe-Co) alloy is widely used due to its strong magnetic properties. However, there is a limit to how much their performance can be improved, necessitating a new approach.

Some earlier studies have shown that epitaxially grown films made up of Fe-Co alloys doped with heavier elements exhibit remarkably high magnetization. Moreover, recent advances in computational techniques, such as the integration of machine learning with ab initio calculations, have significantly accelerated the search for new material compositions.

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In a new publication in Nature Materials, an international team of researchers has developed groundbreaking artificial chains of the iconic “olympicene” molecules to realize the antiferromagnetic (AF) spin-½ Heisenberg model, a flagship quantum spin model that has been the cornerstone of quantum magnetism, since the seminal work of Bethe, for almost a century now. This study makes nanographenes (NGs) an ideal platform for realizing and studying highly entangled quantum spin systems, with potential applications in insulator-based AF spintronics.

In one-dimensional quantum magnets, strong quantum fluctuations prevent spontaneous symmetry breaking, leading to the formation of quantum-disordered many-body states such as resonating valence bond states. Half-integer spin chains are expected to exhibit a gapless spectrum in the thermal dynamic limit, with the elemental excitations comprising at least two fractional spin-½ with well-defined energy-momentum relation, known as spinons.

In finite length, confinement effects introduce a quantization gap, which gradually approaches zero as the chain length increases (L→∞). Despite the theoretical appeal, the experimental realization of the isotropic spin-½ Heisenberg faces significant challenges. Furthermore, the lack of access to well-defined finite chains hampers systematic studies on how spin excitations evolve with chain length and how even-and odd-numbered chains exhibit distinct behaviors.

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A symmetry violation has been observed in a particle-decay process that—together with five related decays—could shed light on the matter–antimatter imbalance in the Universe.

The known Universe has some 1012 galaxies that are made out of matter and no galaxies that are made out of antimatter. This is a surprising result because matter and antimatter are expected to exist in equal quantities. More formally, matter and antimatter are related by a symmetry known as CP symmetry, which states that a particle and its antiparticle should obey the same laws of nature. A necessary condition for the observed imbalance between matter and antimatter in the Universe is therefore a violation of CP symmetry—for a review see H. R. Quinn and Y. Nir [1]. Solving this puzzle has driven extensive experimental efforts that have revealed such a violation in different particle sectors. The Large Hadron Collider Beauty (LHCb) Collaboration at CERN has now measured a CP violation in a certain decay channel of B ±].

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Altermagnets are arguably the hottest objects in magnetism right now (see Viewpoint: Altermagnetism Then and Now). Over the past year, researchers have delivered experimental evidence for this new type of magnet, but they have yet to harness the behavior for applications. Now three independent groups have proposed methods for electrically tuning the properties of altermagnets [1– 3]. If implemented, the findings could allow the use of altermagnets in next-generation spintronics devices.

Altermagnets can be thought of as a cross between antiferromagnets and ferromagnets. Like antiferromagnets the materials lack net magnetization—the magnetic spins of the atomic lattice are aligned in opposing directions. Like ferromagnets they have magnetically sensitive energy levels and display electronic band structures that are split into spin-up and spin-down bands. This splitting can be used to polarize an electronic current, as one spin state will flow through the material more easily. The combination of these properties could allow researchers to create spintronics devices that operate more rapidly and with greater efficiency than those currently in use, but for that, they first need a way to manipulate the spin properties of an altermagnet.

The proposed methods of the three teams (a group led by Tong Zhou of the Eastern Institute of Technology, Ningbo, China; Libor Šmejkal of the Max Planck Institute for the Physics of Complex Systems, Germany; and a group led by Qihang Liu of the Southern University of Science and Technology, China) all use electric fields for this switching. Controlling magnetism with electricity is particularly attractive because electric fields are much easier to manipulate and integrate into modern electronic devices than magnetic fields. Electrical tuning is potentially also faster (subnanosecond) and could use less energy, two crucial properties for the development of high-speed, low-power spintronic devices.

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Time crystals realized in the so-called quasiperiodic regime hold promise for future applications in quantum computing and sensing.

In ordinary crystals, atoms or molecules form a repeating pattern in space. By extension, in quantum systems known as time crystals, particles form a repeating pattern in both space and time. These exotic systems were predicted in 2012 and first demonstrated in 2016 (see Viewpoint: How to Create a Time Crystal). Now Chong Zu at Washington University in St. Louis and his colleagues have experimentally realized a new form of time crystal called a discrete-time quasicrystal [1]. The team suggests that such states could be useful for high-precision sensing and advanced signal processing.

Conventional time crystals are created by subjecting a collection of particles to an external driving force that is periodic in time. Zu and his colleagues instead selected a quasiperiodic drive in the form of a structured but nonrepeating sequence of microwave pulses. The researchers applied this quasiperiodic drive to an ensemble of strongly interacting spins associated with structural defects, known as nitrogen-vacancy centers, in diamond. They then tracked the resulting dynamics of these spins using a laser microscope.

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Scientists have devised a way to store and read data from individual atoms embedded in tiny crystals only a few millimeters in size (where 1 mm is 0.04 inches). If scaled up, it could one day lead to ultra-high density storage systems capable of holding petabytes of data on a single disc — where 1 PB is equivalent to approximately 5,000 4K movies.

Encoding data as 1s and 0s is as old as the entire history of computing, with the only difference being the medium used to store this data — moving from vacuum tubes flashing on and off, tiny electronic transistors, or even compact discs (CDs), with pits in the surface representing 1s and smoothness indicating 0.

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Using the Multi-frequency High Field Electron Spin Resonance Spectrometer at the Steady-State High Magnetic Field Facility (SHMFF), researchers observed the first-ever Bose–Einstein condensation (BEC) of a two-magnon bound state in a magnetic material. The facility is in the Hefei Institutes of Physical Science of the Chinese Academy of Sciences and includes a research team from Southern University of Science and Technology, Zhejiang University, Renmin University of China, and the Australian Nuclear Science and Technology Organization.

This discovery was published in Nature Materials.

BEC is a fascinating quantum phenomenon where particles, typically bosons, condense into a single collective state at ultra-low temperatures. While this effect has been seen in cold atoms, it had never been observed in a magnetic system until now.

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For decades, scientists believed that lead-208, a “doubly magic” and highly stable atomic nucleus, was perfectly spherical. However, groundbreaking new research has shattered this assumption, revealing that its nucleus is actually elongated, much like a rugby ball.

By using an advanced gamma-ray spectrometer and high-speed particle collisions, researchers uncovered unexpected quantum behavior that contradicts long-standing nuclear theory. This revelation forces physicists to rethink fundamental principles of nuclear structure, potentially reshaping our understanding of heavy elements and their formation in the universe.

Lead-208: A Surprising Discovery

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In a megascience-scale collaboration with French researchers from College de France and the University of Montpellier, Skoltech scientists have shown a much-publicized problem with next-generation lithium-ion batteries to have been induced by the very experiments that sought to investigate it. Published in Nature Materials, the team’s findings suggest that the issue of lithium-rich cathode material deterioration should be approached from a different angle, giving hope for more efficient lithium-ion batteries that would store some 30% more energy.

Efficient energy storage is critical for the transition to a low-carbon economy, whether in grid-scale applications, electric vehicles, or portable devices. Lithium-ion batteries remain the best-developed electrochemical storage technology and promise further improvements. In particular, next-generation batteries with so-called lithium-rich cathodes could store about one-third more energy than their state-of-the-art counterparts with cathodes made of lithium nickel manganese cobalt oxide, or NMC.

A key challenge hindering the commercialization of lithium-rich batteries is voltage fade and capacity drop. As the battery is repeatedly charged and discharged in the course of normal use, its cathode material undergoes degradation of unclear nature, causing gradual voltage and capacity loss. The problem is known to be associated with the reduction and oxidation of the in NMC, but the precise nature of this redox process is not understood. This theoretical gap undermines the attempts to overcome voltage fade and bring next-generation batteries to the market.

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In a recent collaboration between the High Magnetic Field Center of the Hefei Institutes of Physical Science of Chinese Academy of Sciences, and the University of Science and Technology of China, researchers introduced the concept of the topological Kerr effect (TKE) by utilizing the low-temperature magnetic field microscopy system and magnetic force microscopy imaging system supported by the steady-state high magnetic field experimental facility.

The findings, published in Nature Physics, hold significant promise for advancing our understanding of topological magnetic structures.

Originating in , skyrmions represent unique topological excitations found in condensed matter . These structures, characterized by their vortex or ring-like arrangement of spins, possess non-trivial properties that make them potential candidates for next-generation magnetic storage and logic devices.

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