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Category: particle physics – Page 4

Atom tweezer arrays reveal how phase transitions unfold in mesoscopic systems

As the number of particles in a physical system increases, its properties can change and different phase transitions (i.e., shifts into different phases of matter) can take place. Microscopic systems (i.e., containing only a few particles) and macroscopic ones (i.e., containing many particles) are thus typically very different, even if the types of particles they are made up of are the same.

Mesoscopic systems lie somewhere between microscopic and macroscopic systems, as they are small enough for individual particle fluctuations to impact their dynamics and yet large enough to support collective particle dynamics. Studying these middle-sized physical systems can yield interesting insight into how the fluctuations of individual particles can give rise to the collective particle behavior observed as a system grows.

Researchers at the University of California Berkeley and Columbia University recently introduced a new approach to precisely realize physical systems that are ideal for studying mesoscopic physics and the underpinnings of phase transitions. Their approach, outlined in a paper published in Nature Physics, relies on the use of atom tweezer arrays to control the number of atoms in a system and how they interact with light.

Scientists Achieve “Impossible” Feat in Quantum Measurement

CU Boulder scientists created a quantum device that uses cold atoms and lasers to track 3D acceleration. In a new study, physicists at the University of Colorado Boulder used a cloud of atoms cooled to extremely low temperatures to measure acceleration in three dimensions at the same time, achiev

Scientists Create Exotic “Anyons” in One-Dimensional Quantum Gas

The answer, it turns out, is yes. In a breakthrough experiment, scientists have observed signs of anyons in a one-dimensional ultracold gas for the first time. The research, published in Nature, involved teams from the University of Innsbruck, Université Paris-Saclay, and Université Libre de Bruxelles.

To reveal the presence of anyons, the scientists carefully injected and accelerated a mobile impurity into a tightly controlled gas of bosons at near absolute zero.

Absolute zero is the theoretical lowest temperature on the thermodynamic scale, corresponding to 0.00 K (−273.15 °C or −459.67 °F). At this point, atomic motion ceases entirely, and the substance no longer emits or absorbs thermal energy.

Muon Beams Manipulated

Researchers have demonstrated the slowing and subsequent reacceleration of a muon beam, increasing the potential of muon beams as a research tool.

About every second, the average human has a rare messenger from the edge of space passing through their body. Muons―similar to electrons but with 200 times the mass―are created naturally when cosmic ions strike the upper atmosphere, producing a shower of particles. Muons can also be created artificially, but these muon beams are very sparse compared to more conventional electron, proton, and ion beams. Over the past few decades, researchers have developed a way to make much denser beams [1, 2], but the difficulty of working with such beams has kept scientists from fulfilling their potential as a research tool. Now a team at the Japan Proton Accelerator Research Complex (J-PARC) has successfully demonstrated the capability to manipulate a dense muon beam, accelerating the muons in a radio-frequency device for the first time [3].

Dramatic stretch in quantum materials confirms 100-year-old prediction

Research from the University of St Andrews has set a new benchmark for the precision with which researchers can explore fundamental physics in quantum materials. The work has implications extending from materials science to advanced computing, as well as confirming a nearly 100-year-old prediction.

The researchers explored magnetoelastic coupling, which is the change in the size or shape of a material when exposed to a . It is usually a small effect, but one that has technological consequences.

A team from the School of Physics and Astronomy at the University of St Andrews has now discovered that this effect is remarkably large in a case where one wouldn’t have expected it—in a transition metal oxide. Oxides are a containing at least one and one other element in its chemical formula. High-temperature superconductors are one of the most prominent examples of a transition metal oxide.

Astronomers are Closing in on the Source of Galactic Cosmic Rays

In 1912, astronomer Victor Hess discovered strange, high-energy particles known as “cosmic rays.” Since then, researchers have hunted for their birthplaces. Today, we know about some of the cosmic ray “launch pads”, ranging from the Sun and supernova explosions to black holes and distant active galactic nuclei. What astronomers are now searching for are sources of cosmic rays within the Milky Way Galaxy.

In a pair of presentations at the recent American Astronomical Society meeting, a team led by Michigan State University’s Zhuo Zhang, proposed an interesting place where cosmic rays originate: a pulsar wind nebula in our own Milky Way Galaxy. A pulsar is a rapidly rotating neutron star, formed as a result of a supernova explosion. High-energy particles and the neutron star’s strong magnetic field combine to interact with the nearby interstellar medium. The result is a pulsar wind nebula that can be detected across nearly the whole electromagnetic spectrum, particularly in X-rays. It makes sense that this object would be a source of cosmic rays. Pulsars are found throughout the Galaxy, which makes them a useful category in the search for cosmic ray engines in the Milky Way.

The Vela Pulsar is a good example of a pulsar wind nebula. The pulsar is at the center, and the surrounding cloudiness is the nebula. Courtesy NASA.
The Vela Pulsar is a good example of a pulsar wind nebula. The pulsar is at the center, and the surrounding cloudiness is the nebula. Courtesy NASA.

Ultra-thin metallic oxide reveals unexpected magnetic behavior for spintronic applications

In a new study, researchers at the University of Minnesota Twin Cities discovered surprising magnetic behavior in one of the thinnest metallic oxide materials ever made. This could pave the way for the next generation of faster and smarter spintronic and quantum computing devices.

New Material Breaks the Rules: Scientists Turn Insulator Into a Semiconductor

Once considered merely insulating, a change in the angle between silicon and oxygen atoms opens a pathway for electrical charge to flow.

A breakthrough discovery from the University of Michigan has revealed that a new form of silicone can act as a semiconductor. This finding challenges the long-held belief that silicones are only insulating materials.

“The material opens up the opportunity for new types of flat panel displays, flexible photovoltaics, wearable sensors or even clothing that can display different patterns or images,” said Richard Laine, U-M professor of materials science and engineering and macromolecular science and engineering and corresponding author of the study recently published in Macromolecular Rapid Communications.

Crystal melting and the glass transition obey the same physical law

The melting of crystals is the process by which an increase in temperature induces the disruption of the ordered crystalline lattice, leading to the disordered structure and highly fluctuating dynamic behavior of liquids. At the glass transition, where an amorphous solid (a glass) turns into a liquid, there is no obvious change in structure, and only the dynamics of the atoms change, going from strongly localized dynamics in space (in the glass state) to the highly fluctuating (diffusive) dynamics in the liquid.

The search for the atomic-scale mechanism of 3D crystal melting has a long history in physics, and famous physicists such as Max Born, Neville Mott and Frederick Lindemann proposed different ways to look at it. I have always had the impression that we still do not understand the melting of 3D crystals, which is a highly complicated cooperative process involving nonlinearly coupled dynamics of a huge number of atoms. This complexity I always found very fascinating.

Comparatively, the melting of 2D solids, mediated by dislocations-unbinding, is much better understood, and the theory that describes it led to the 2017 Nobel prize in physics for Kosterlitz and Thouless.