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Category: particle physics – Page 537

Circa 2014

Scientists may soon create matter entirely from light, using technology that is already available to complete a quest 80 years in the making.

The experiment would re-create events that were critical in the first 100 seconds of the universe and that are also expected to happen in gamma-ray bursts, the most powerful explosions in the cosmos and one of the greatest unsolved mysteries in physics, researchers added.

As Einstein’s famous equation E=mc proved, mass can get converted into energy and vice versa. For instance, when an electron meets its antimatter counterpart, a positron, they annihilate each other, releasing photons, the particles making up light.

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In our daily lives, we can find many examples of manipulation of reflected waves such as mirrors to see our reflections or reflective surfaces for sound that improve auditorium acoustics. When a wave impinges on a reflective surface with a certain angle of incidence and the energy is sent back, the angle of reflection is equal to the angle of incidence. This classical reflection law is valid for any homogenous surface. Researchers at Aalto University have developed new metasurfaces for the arbitrary manipulation of reflected waves, essentially breaking the law to engineer the reflection of a surface at will.

Metasurfaces are artificial structures, composed of periodic arranged of meta-atoms at subwavelength scale. Meta-atoms are made of traditional materials but, if they are placed in a periodic manner, the surface can show many unusual effects that cannot be realized by the materials in nature. In their article published 15 February 2019 in Science Advances, the researchers use power-flow conformal metasurfaces to engineer the direction of reflected waves.

‘Existing solutions for controlling reflection of waves have low efficiency or difficult implementation,’ says Ana Díaz-Rubio, postdoctoral researcher at Aalto University. ‘We solved both of those problems. Not only did we figure out a way to design high efficient metasurfaces, we can also adapt the design for different functionalities. These metasurfaces are a versatile platform for arbitrary control of reflection.’

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Imagine if we could replace fossil fuels with our very own stars. And no, we’re not talking about solar power: We’re talking nuclear fusion. And recent research is helping us get there. Meet the Experimental Advanced Superconducting Tokamak, or EAST.

EAST is a fusion reactor based in Hefei, China. And it can now reach temperatures more than six times as hot as the sun. Let’s take a look at what’s happening inside. Fusion occurs when two lightweight atoms combine into a single, larger one, releasing energy in the process. It sounds simple enough, but it’s not easy to pull off. Because those two atoms share a positive charge. And just like two opposing magnets, those positive atoms repel each other.

Stars, like our sun, have a great way of overcoming this repulsion … their massive size, which creates a tremendous amount of pressure in their cores … So the atoms are forced closer together making them more likely to collide. There’s just one problem: We don’t have the technology to recreate that kind of pressure on Earth.

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Despite the young age of the research field, substantial progress has been made in the study of metal halide perovskite nanocrystals (HPNCs). Just as their thin-film counterparts are used for light absorption in solar cells, they are on the way to revolutionizing research on novel chromophores for light emission applications. Exciting physics arising from their peculiar structural, electronic, and excitonic properties are being discovered with breathtaking speed. Many things we have learned from the study of conventional semiconductor quantum dots (CSQDs) of II–VI (e.g., CdSe), IV–VI (e.g., PbS), and III–V (e.g., InP) compounds have to be thought over, as HPNCs behave differently. This Feature Article compares both families of nanocrystals and then focuses on approaches for substituting toxic heavy metals without sacrificing the unique optical properties as well as on surface coating strategies for enhancing the long-term stability.

In the early 1980s the quest for novel photocatalysts, fueled by the oil crisis in the preceding decade, led to the discovery of semiconductor quantum dots. Pioneering works by Efros, Brus, and Henglein showed both experimentally and theoretically that the reduction of size of semiconductor particles (e.g., CdS) down to the nanometer range induces a significant change in their band gap energy.(1−3) The underlying quantum confinement effect, occurring when the nanocrystal size is (significantly) smaller than twice the exciton Bohr radius of the semiconductor material (Table 1), leads to an increase, scaling with 1/r, of the band gap energy. It also gives rise to the appearance of discrete energy levels at the place of continuous valence and conduction energy bands. In the same period Ekimov as well as Itoh and co-workers observed quantum confinement in small CuCl crystallites embedded in a glass or a NaCl matrix.

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By ricocheting neutrons off the atoms of yttrium manganite (YMnO3) heated to 3,000 degrees Fahrenheit, researchers have discovered the atomic mechanisms that give the unusual material its rare electromagnetic properties. The discovery could help scientists develop new materials with similar properties for novel computing devices and micro-actuators.

The experiment was conducted as a collaboration between Duke University and Oak Ridge National Laboratory (ORNL) and appeared online in Nature Communications on January 2, 2018.

Ferromagnetism is the scientific term for the phenomenon responsible for permanent magnets like iron. Such exist because their molecular structure consists of tiny magnetic patches that all point in the same direction. Each patch, or domain, is said to have a , with a north and a south pole, which, added together, produce the magnetic fields so often seen at work on refrigerator doors.

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Electronics rely on the movement of negatively-charged electrons. Physicists strive to understand the forces that push these particles into motion, with the goal of harnessing their power in new technologies. Quantum computers, for instance, employ a fleet of precisely controlled electrons to take on goliath computational tasks. Recently, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) demonstrated how microwaves cut in on the movements of electrons. The findings may contribute to future quantum computing technology.

The logic operations of normal computers are based on zeros and ones, and this binary code limits the volume and type of information the machines can process. Subatomic particles can exist in more than two discrete states, so computers harness to crunch complex data and perform functions at whiplash speed. To keep electrons in limbo for experiments, scientists capture the particles and expose them to forces that alter their behavior.

In the new study, published December 18, 2018 in Physical Review B, OIST researchers trapped electrons in a frigid, vacuum-sealed chamber and subjected them to microwaves. The particles and light altered each other’s movement and exchanged energy, which suggests the sealed system could potentially be used to store quantum information – a microchip of the future.

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The history of the universe is predicated on the idea that, compared to today, the universe was hotter and more symmetric in its early phase. Scientists have thought this because of the Higgs Boson finding—the particle that gives mass to all other fundamental particles. The concept is that as one analyzes time back toward the Big Bang, the universe gets hotter and the Higgs phase changes to one where everything became massless. Now, physicists are presenting a new theory that suggests an alternative history of the universe is possible.

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Possible quantum computing at room temperature. Scientists working with hexagonal boron nitride, which allows them to work in two-dimensional arrays. Simpler than using 3D objects such as diamonds.

Researchers have now demonstrated a new hardware platform based on isolated electron spins in a two-dimensional material. The electrons are trapped by defects in sheets of hexagonal boron nitride, a one-atom-thick semiconductor material, and the researchers were able to optically detect the system’s quantum states.

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