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Category: particle physics – Page 12

Growth strategy enables coherent quantum transport in single-layer MoS₂ semiconductors

Two-dimensional (2D) semiconductors are thin materials (i.e., one-atom thick) with advantageous electronic properties. These materials have proved to be promising for the development of thinner, highly performing electronics, such as fitness trackers and portable devices.

A 2D semiconductor that has attracted particular interest within the electronics community is molybdenum disulfide (MoS₂), a transition-metal dichalcogenide made up of one metal atom and two chalcogen atoms. To build reliable large-area electronics based on MoS₂ layers, engineers need to uniformly grow this material over wafer-scale surfaces, minimizing defects that hinder the performance of devices.

Researchers at the Institute for Basic Science (IBS), Pohang University of Science and Technology (POSTECH) and other institutes recently introduced a new approach to grow single-layer MoS₂ on substrates while maintaining a uniform atomic arrangement. Their approach, outlined in a paper in Nature Electronics, entails a greater control of the process by which small crystal regions merge on a substrate, also known as coalescence.

Real-life ‘quantum molycircuits’ using exotic nanotubes

Molybdenum disulfide MoS2 is a groundbreaking material for electronics applications. As a two-dimensional layer similar to graphene, it is an excellent semiconductor, and can even become intrinsically superconducting under the right conditions. It’s not particularly surprising that science fiction authors have already been speculating about molycircs, fictional computer circuits built from MoS2, for years—and that physicists and engineers are directing huge research efforts at this material.

Researchers at the University of Regensburg, have many years of expertise with diverse quantum materials—in particular also with carbon nanotubes, tube-like macromolecules made from carbon atoms alone.

“It was an obvious next step to now focus on MoS2 and its fascinating properties,” said Dr. Andreas K. Hüttel, head of the research group Nanotube Electronics and Nanomechanics in Regensburg. In cooperation with Prof. Dr. Maja Remškar, Jožef Stefan Institut Ljubljana, a specialist in the crystalline growth of nanomaterials, his research group started working on based on MoS2 nanotubes.

Enlarging the Periodic Table of Laser-Cooled Molecules

A class of molecules with two valence electrons has been laser cooled and trapped for the first time.

Over the past 70 years, physicists have developed laser-based methods for controlling atoms and molecules, but much of this success has been concentrated on a few columns of the periodic table. For molecules, laser cooling has been limited to diatomic species that have a single unpaired valence electron for interacting with light. Extending laser cooling to molecules with two valence electrons has long been sought after (Fig. 1). The most promising nonreactive candidates are diatomic molecules that partner a halogen, such as fluorine (F) or chlorine (Cl), with a p-block atom, such as aluminum (Al) or thallium (Tl). Several research groups have specifically targeted AlF, AlCl, and TlF, but these molecules are difficult to work with because of their deep-ultraviolet transitions, complicated energy-level structures, and small magnetic moments.

Earth’s atmosphere may help support human life on the moon

The moon’s surface may be more than just a dusty, barren landscape. Over billions of years, tiny particles from Earth’s atmosphere have landed in the lunar soil, creating a possible source of life-sustaining substances for future astronauts. But scientists have only recently begun to understand how these particles make the long journey from Earth to the moon and how long the process has been taking place.

New research from the University of Rochester, published in Communications Earth & Environment, shows that Earth’s magnetic field may actually help guide atmospheric particles—carried by solar wind—into space, instead of blocking them. Because Earth’s magnetic field has existed for billions of years, this process could have steadily moved particles from Earth to the moon over very long periods of time.

“By combining data from particles preserved in lunar soil with computational modeling of how solar wind interacts with Earth’s atmosphere, we can trace the history of Earth’s atmosphere and its magnetic field,” says Eric Blackman, a professor in the Department of Physics and Astronomy and a distinguished scientist at URochester’s Laboratory for Laser Energetics (LLE).

Magic moments with John Bell

This was a monumental breakthrough in the philosophy and foundations of quantum mechanics. Bell derived a mathematical inequality that showed if there were any local “hidden variables” (underlying, deterministic factors) explaining the “spooky” correlations in quantum entanglement, those correlations would have to obey certain limits. Experiments inspired by his theorem (starting with Alain Aspect in the early 1980s) have repeatedly shown that these limits are violated, confirming that quantum entanglement is real, non-local, and that nature fundamentally disagrees with Einstein’s idea of “local realism.”

John Bell, with whom I had a fruitful collaboration and warm friendship, is best known for his seminal work on the foundations of quantum physics, but he also made outstanding contributions to particle physics and accelerator physics.

Neutrino observatories show promise for detecting light dark matter

Dark matter is an elusive type of matter that does not emit, reflect or absorb light, yet is estimated to account for most of the universe’s mass. Over the past decades, many physicists worldwide have been trying to detect this type of matter or signals associated with its presence, employing various approaches and technologies.

As it has never been directly detected before, the composition and properties of dark matter remain mostly unknown. Initially, dark matter searches focused on the detection of relatively heavy particles. More recently, however, physicists also started looking for lighter particles with masses below one giga-electron-volt (GeV), which would thus be lighter than protons.

Researchers at SLAC National Accelerator Laboratory and The Ohio State University recently showed that signatures of these sub-GeV dark matter particles could also be picked up by neutrino observatories, large underground detectors originally designed to study neutrinos (i.e., light particles that weakly interact with regular matter).

Ghostly solar neutrinos caught transforming carbon atoms deep underground

Neutrinos are one of the most mysterious particles in the universe, often called “ghost particles” because they rarely interact with anything else. Trillions stream through our bodies every second, yet leave no trace. They are produced during nuclear reactions, including those that take place in the core of our sun.

Their tendency to not interact often makes detecting neutrinos notoriously difficult. Neutrinos from the sun have only been seen to interact on a handful of different targets. Now, for the first time, scientists have succeeded in observing them transform carbon atoms into nitrogen inside a vast underground detector.

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