Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: particle physics – Page 331

A matter-wave interferometer can probe the magnetism of a broad range of species, from single atoms to very large, weakly magnetic molecules.

This year marks the centenary of the ground-breaking experiment of Otto Stern and Walther Gerlach that demonstrated the quantization of the spin angular momentum of an atom [1]. The evidence came from the observation that a beam of silver atoms, upon traversing a spatially varying magnetic field, split into two beams. The spatial splitting of the spin-up and spin-down atoms corresponded to an atomic magnetic moment of 1 Bohr magneton—the magnetic moment of a single spinning electron. The deflection of particle beams in a spatially varying magnetic field remains the basis of techniques for characterizing the magnetic properties of isolated atoms and molecules. Such techniques, however, aren’t sufficiently sensitive to study very large, weakly magnetic molecules, including many biological molecules.

Read more | >

Topological materials that possess certain atomic-level symmetries, including topological insulators and topological semi-metals, have elicited fascination among many condensed matter scientists because of their complex electronic properties. Now, researchers in Japan have demonstrated that a normal semiconductor can be transformed into a topological semi-metal by light irradiation. Further, they showed how spin-dependent responses could appear when illuminated with circularly-polarized laser light. Published in Physical Review B, this work explores the possibility of creating topological semi-metals and manifesting new physical properties by light control, which may open up a rich physical frontier for topological properties.

Most ordinary substances are either , like metals, or insulators, like plastic. In contrast, can exhibit unusual behavior in which electrical currents flow along the surface of the sample, but not inside the interior. This characteristic behavior is strongly connected to topological properties inherent in the electronic state. Furthermore, a novel phase called a topological semi-metal provides a new playground for exploring the role of topology in condensed matter. However, the underlying physics of these systems is still being pondered.

Researchers at the University of Tsukuba studied the dynamics of excitations in zinc arsenide (Zn3As2) when irradiated with a laser with circular polarization. Zinc arsenide is normally thought of as a narrow-gap semiconductor, which means that electrons are not free to move around on their own but can be easily propelled by energy from an external light source. Under the right conditions, the material can show a special topological state called a “Floquet-Weyl semi-metal,” which is a topological semi-metal coupled with light. In this case, the can be carried in the form of quasiparticles called Weyl fermions. Because these quasiparticles travel as if they have zero mass and resist becoming scattered, Weyl fermions can move easily through the material.

Read more | >

face_with_colon_three circa 2018.

Understanding the fundamental constituents of the universe is tough. Making sense of the brain is another challenge entirely. Each cubic millimetre of human brain contains around 4 km of neuronal “wires” carrying millivolt-level signals, connecting innumerable cells that define everything we are and do. The ancient Egyptians already knew that different parts of the brain govern different physical functions, and a couple of centuries have passed since physicians entertained crowds by passing currents through corpses to make them seem alive. But only in recent decades have neuroscientists been able to delve deep into the brain’s circuitry.

On 25 January, speaking to a packed audience in CERN’s Theory department, Vijay Balasubramanian of the University of Pennsylvania described a physicist’s approach to solving the brain. Balasubramanian did his PhD in theoretical particle physics at Princeton University and also worked on the UA1 experiment at CERN’s Super Proton Synchrotron in the 1980s. Today, his research ranges from string theory to theoretical biophysics, where he applies methodologies common in physics to model the neural topography of information processing in the brain.

“We are using, as far as we can, hard mathematics to make real, quantitative, testable predictions, which is unusual in biology.” — Vijay Balasubramanian

Read more | >

The Standard Model is our best theory for how the universe operates, but there are some missing pieces that physicists are struggling to find.

The Standard Model of physics is the theory of particles, fields and the fundamental forces that govern them.

It tells us about how families of elementary particles group together to form larger composite particles, and how one particle can interact with another, and how particles respond to the fundamental forces of nature. It has made successful predictions such as the existence of the Higgs boson, and acts as the cornerstone for theoretical physics.

Read more | >

Even in the driest climates, though, there is a considerable amount of moisture in the air. The researchers note that even in places like the Sahel desert, relative humidity is still around 20 percent on average. So they set about finding a way to use this untapped water resource to produce hydrogen.

Their device consists of a water harvesting unit that houses a sponge soaked in a water-absorbing liquid that can pull moisture from the air. On either side of this reservoir are electrodes that can be powered by any renewable energy source. When a current runs through the circuit, the water is split via electrolysis into its constituent oxygen and hydrogen atoms, which can then be collected as gas.

The team showed that the device could run efficiently for 12 consecutive days and produced hydrogen with 99 percent purity. What’s more, the device continues to work in relative humidity as low as four percent.

Read more | >

Circa 2021 face_with_colon_three

Metallic non-metals

In theory, most materials are capable of becoming metallic if put under enough pressure. Atoms or molecules can be squeezed together so tightly that they begin to share their outer electrons, which can then travel and conduct electricity as they do in a chunk of copper or iron. Geophysicists think that the centres of massive planets such as Neptune or Uranus host water in such a metallic state, and that high-pressure metallic hydrogen can even become a superconductor, able to conduct electricity without any resistance.

Turning water into a metal in this way would require an expected 15 million atmospheres of pressure, which is out of reach for current lab techniques, says Jungwirth. But he suspected that water could become conductive in an alternative way: by borrowing electrons from alkali metals. These reactive elements in group 1 of the periodic table, which includes sodium and potassium, tend to donate their outermost electron. Last year, Jungwirth and his colleague Phil Mason — a chemist who is also known for making science videos on YouTube — led a team that demonstrated a similar effect in ammonia2. The fact that ammonia can turn shiny in such conditions was known to the British chemist Humphry Davy in the early nineteenth century, Edwards points out.

Read more | >

Many of us are all too familiar with how strain in work relationships can impact performance, but new research shows that materials in electricity-producing fuel cells may be sensitive to strain on an entirely different level.

Researchers from Kyushu University report that strain caused by just a 2% reduction in the distance between atoms when deposited on a surface leads to a whopping 99.999% decrease in the speed at which the materials conduct , greatly reducing the performance of solid oxide cells.

Developing methods to reduce this strain will help bring high-performance fuel cells for clean energy production to a wider number of households in the future.

Read more | >