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Category: particle physics – Page 123

Argonne’s Science 101 series takes you back to the basics, with plain-language explanations of the scientific concepts behind our pivotal discoveries and our biggest innovations.

In this Science 101 video, postdoctoral researchers Gillian Beltz-Mohrmann and Florian Kéruzoré explore two of the biggest mysteries in science: dark matter and dark energy. These strange influences seem to be stretching the universe apart and clumping stuff together in unexpected ways. Together, they make up a whopping 95% of the universe, but because we can’t see or touch them, we don’t know what they are.

Researchers around the globe, including scientists at the U.S. Department of Energy’s Argonne National Laboratory, are investigating the nature of dark matter and dark energy through large cosmological surveys, particle physics experiments and advanced computing and simulation.

Find out more about Argonne Science 101 ►► https://www.anl.gov/science-101

Continue reading “Science 101: What are Dark Matter and Dark Energy?” | >

‘Opposites charges attract; like charges repel’ is a fundamental principle of basic physics. But a new study from Oxford University, published in Nature Nanotechnology (“A charge-dependent long-ranged force drives tailored assembly of matter in solution”), has demonstrated that similarly charged particles in solution can, in fact, attract each other over long distances. Just as surprisingly, the team found that the effect is different for positively and negatively charged particles, depending on the solvent.

The study found that negatively charged silica microparticles suspended in water attracted each other to form hexagonally arranged clusters. (Image: Zhang Kang)

Besides overturning long-held beliefs, these results have immediate implications for a range of processes that involve interparticle and intermolecular interactions across various length-scales, including self-assembly, crystallisation, and phase separation.

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Experiments demonstrate some of the unusual features of molecular reactions that occur in the deep cold of interstellar space.

Many common small molecules are formed in interstellar space, and their low temperatures are expected to have profound effects on their chemical reactions because of quantum-mechanical effects that are masked at higher temperatures. Researchers have now demonstrated some of these cold chemistry phenomena—such as the effects of molecular rotation and collision energy on reaction rates—in a reaction between a hydrogen ion and an ammonia molecule in the lab. The results, while intuitively surprising at first glance, can be explained by a careful theoretical analysis of the quantum chemistry.

Measuring reaction rates at low temperatures is useful for testing quantum-chemical theory because in those conditions molecules may occupy only a few well-defined quantum states. Such experiments could also offer insights into chemical processes in the cold clouds of gas in star-forming regions of interstellar space, where many of the simple molecules that make up solar systems are formed. But low-temperature experiments are difficult, especially for charged atoms and molecules (ions), because they are very sensitive to stray electric fields in the environment, which accelerate and heat up the ions.

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You may never have heard of magnetars, but they are, in a nutshell an exotic type of neutron star whose magnetic field is around a trillion times stronger than the Earth’s.

To illustrate their strength, if you were to get any closer to a magnetar than about 1,000km (600 miles) away, your body would be totally destroyed.

Its unimaginably powerful field would tear electrons away from your atoms, converting you into a cloud of monatomic ions – single atoms without electrons– as EarthSkynotes.

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As silicon-based computer chips approach their physical limitations in the quest for faster and smaller designs, the search for alternative materials that remain functional at atomic scales is one of science’s biggest challenges.

In a groundbreaking development, researchers at the Würzburg-Dresden Cluster of Excellence have engineered a protective film that shields quantum semiconductor layers just one atom thick from environmental influences without compromising their revolutionary quantum properties. This puts the application of these delicate atomic layers in ultrathin within realistic reach. The findings have been published in Nature Communications.

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A small combined team of material scientists from Sun Yat-sen University and Dalian University of Technology, both in China, has found that it is possible to make a single drop of water hop in desired ways by putting a magnetic particle inside of it and turning an electromagnet on and off. The research published in the journal ACS Nano.

The research team was investigating on-demand droplet transportation as part of a larger effort. To learn more about the possibility of inciting drops of liquid, in this case water, to move in desired ways, they set up several structures.

The researchers carved small grooves on a . The surface was then covered with a varnish known to prevent water absorption, thereby allowing droplets to form when splashed onto the surface. Once the droplets formed, the team placed a tiny piece of metal into each drop, where it was held in place by the forces that held the bubble shape. The entire surface was then placed over a set of electromagnets.

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Hydrogen (like many of us) acts weird under pressure. Theory predicts that when crushed by the weight of more than a million times our atmosphere, this light, abundant, normally gaseous element first becomes a metal, and even more strangely, a superconductor—a material that conducts electricity with no resistance.

Scientists have been eager to understand and eventually harness superconducting hydrogen-rich compounds, called hydrides, for practical applications—from levitating trains to particle detectors. But studying the behavior of these and other materials under enormous, sustained pressures is anything but practical, and accurately measuring those behaviors ranges somewhere between a nightmare and impossible.

Like the calculator did for arithmetic, and ChatGPT has done for writing five-paragraph essays, Harvard researchers think they have a foundational tool for the thorny problem of how to measure and image the behavior of superconductors at high pressure.

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Quantum materials have generated considerable interest for computing applications in the past several decades, but non-trivial quantum properties—like superconductivity or magnetic spin—remain in fragile states.

“When designing quantum materials, the game is always a fight against disorder,” said Robert Hovden, an associate professor of materials science and engineering at the University of Michigan.

Heat is the most common form of disorder that disrupts quantum properties. Quantum materials often only exhibit exotic phenomena at very low temperatures when the atom nearly stops vibrating, allowing the surrounding electrons to interact with one another and rearrange themselves in unexpected ways. This is why quantum computers are currently being developed in baths of liquid helium at −269 °C, or around −450 F. That’s just a few degrees above zero Kelvin (−273.15 °C).

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Enhancing quantum features compensates for environmental losses, amplifying particle interactions, achieving entanglement at higher scales.

One of the oldest topics of contemporary science is where to draw the line between classical and quantum physics.

Abstract

The ability to engineer cavity-mediated interactions has emerged as a powerful tool for the generation of non-local correlations and the investigation of non-equilibrium phenomena in many-body systems. Levitated optomechanical systems have recently entered the multi-particle regime, with promise for using arrays of massive strongly coupled oscillators for exploring complex interacting systems and sensing. Here, by combining advances in multi-particle optical levitation and cavity-based quantum control, we demonstrate, for the first time, programmable cavity-mediated interactions between nanoparticles in a vacuum. The interaction is mediated by photons scattered by spatially separated particles in a cavity, resulting in strong coupling (Gzz/Ωz = 0.238 ± 0.005) that does not decay with distance within the cavity mode volume. We investigate the scaling of the interaction strength with cavity detuning and inter-particle separation and demonstrate the tunability of interactions between different mechanical modes. Our work paves the way towards exploring many-body effects in nanoparticle arrays with programmable cavity-mediated interactions, generating entanglement of motion, and using interacting particle arrays for optomechanical sensing.

Continue reading “Scientists create dancing nanoparticles to explore quantum limitations” | >