Researchers have precisely measured the electrical-transport properties of a highly ordered Wigner solid—a crystalline state formed of electrons rather than atoms.
When Emiliano Cortés goes hunting for sunlight, he doesn’t use gigantic mirrors or sprawling solar farms. Quite the contrary, the professor of experimental physics and energy conversion at LMU dives into the nanocosmos.
“Where the high-energy particles of sunlight, the photons, meet atomic structures is where our research begins,” Cortés says. “We are working on material solutions to capture and use solar energy more efficiently.”
His findings have great potential as they enable novel solar cells and photocatalysts. The industry has high hopes for the latter because they can make light energy accessible for chemical reactions—bypassing the need to generate electricity. But there is one major challenge to using sunlight, which solar cells also have to contend with, Cortés knows: “Sunlight arrives on Earth ‘diluted,’ so the energy per area is comparatively low.” Solar panels compensate for this by covering large areas.
Long before the Deep Underground Neutrino Experiment takes its first measurements in an effort to expand our understanding of the universe, a prototype for one of the experiment’s detectors is blazing new trails in neutrino detection technology.
DUNE, currently under construction, will be a massive experiment that spans more than 800 miles. A beam of neutrinos originating at the U.S. Department of Energy’s Fermi National Accelerator Laboratory will pass through a particle detector located on the Fermilab site, then travel through the ground to a huge detector at the Sanford Underground Research Facility in South Dakota.
The near detector consists of a set of particle detection systems. One of them, known as the ND-LAr, will feature a liquid-argon time projection chamber to record particle tracks; it will be placed inside a container full of liquid argon. When a neutrino collides with one of the particles that make up argon atoms, the collision generates more particles. As each particle created in the collision travels out of the nucleus, it interacts with nearby atoms, stripping off some of their electrons, leading to the production of detectable signals in the form of light and charge.
A first-principles model accounts for the wide range of critical temperatures (Tc’s) for four materials and suggests a parameter that determines Tc in any high-temperature superconductor.
Since the first high-temperature superconducting materials, known as the cuprates, were discovered in 1986, researchers have struggled to explain their properties and to find materials with even higher superconducting transition temperatures (Tc’s). One puzzle has been the cuprates’ wide variation in Tc, ranging from below 10 K to above 130 K. Now Masatoshi Imada of Waseda University in Japan and his colleagues have used first-principles calculations to determine the order parameters—which measure the density of superconducting electrons—for four cuprate materials and have predicted the Tc’s based on those order parameters [1]. The researchers have also found what they believe is the fundamental parameter that determines Tc in a given material, which they hope will lead to the development of higher-temperature superconductors.
For each material, Imada and his colleagues applied the basic principles of quantum mechanics, focusing on the planes of copper and oxygen atoms that are known to host the superconducting electrons. They used a combination of numerical techniques, including one supplemented by machine learning, and did not require any adjustable parameters.
A measurement of the charge radius of an aluminum nucleus probes the assumption that there are only three families of quarks.
In the standard model of particle physics, matter is made of elementary particles called quarks and leptons. Quarks are the heavy constituents that form, for example, protons and neutrons, whereas leptons are the light constituents, such as the electron. The six known quarks—up, down, charm, strange, top, and bottom—are split into three families. But could there be a fourth family? Answering that question would require hundreds of different measurements in particle and nuclear physics. However, not all these measurements are yet available or precise enough, and many parameter values are only inferred or extrapolated. Now Peter Plattner at CERN in Switzerland and his colleagues show how a single one of these measurements can shift our understanding of this fundamental question [1].
In the quantum-mechanical framework of the standard model, quarks can oscillate among their different flavors. The best-known example occurs in the beta decay of radioactive nuclei: a proton is transformed into a neutron (or vice versa) when one of its quarks oscillates from up to down (or down to up). The rate of beta decay depends on many factors involving both nuclear and atomic physics, but the rate at which the quarks oscillate is described by a single quantity: Vud, the so-called matrix element of the transformation of an up quark into a down quark.
On July 21, 2017, a group of dignitaries, scientists and engineers gathered in Lead, South Dakota, to hold a unique groundbreaking ceremony—at a research institution in a former gold mine, about one mile underground. The ceremony marked the beginning of construction for the Deep Underground Neutrino Experiment.
DUNE will study neutrinos, fundamental particles of matter that are abundant across the universe but difficult to catch. Over 100 trillion of them flow harmlessly and undetectably through your body each second.
Neutrinos come in three flavors—electron neutrinos, muon neutrinos and tau neutrinos—and they oscillate between those flavors as they travel. This means that a neutrino first produced as an electron neutrino can become a muon or tau neutrino.
In the basement of Kirchhoff-Institut für Physik in Germany, researchers have been simulating the Universe as it might have existed shortly after the Big Bang. They have created a tabletop quantum field simulation that involves using magnets and lasers to control a sample of potassium-39 atoms that is held close to absolute zero. They then use equations to translate the results at this small scale to explore possible features of the early Universe.
The work done so far shows that it’s possible to simulate a Universe with a different curvature. In a positively curved universe, if you travel in any direction in a straight line, you will come back to where you started. In a negatively curved universe, space is bent in a saddle shape. The Universe is currently flat or nearly flat, according to Marius Sparn, a PhD student at Kirchhoff-Institut für Physik. But at the beginning of its existence, it might have been more positively or negatively curved.
Physicists are coming to realise that hypothetical particles called axions could explain not only dark matter, but dark energy too, and more besides. Now there is fresh impetus to detect them.
Particle accelerators are hugely useful in scientific research, but – like the Large Hadron Collider (LHC) – usually take up vast amounts of room. A remarkable new system developed at the University of Texas in Austin could change this.
In experiments, researchers were able to use their particle accelerator to generate an electron beam with an energy of 10 billion electron volts (10 GeV) in a chamber measuring just 10 centimeters (4 inches).
The complete instrument measures 20 meters (66 feet) from end to end. In comparison, other particle accelerators that can generate 10 GeV beams are some 3 kilometers (almost 2 miles) in length – about 150 times as long.
More stable clocks could measure quantum phenomena, including the presence of dark matter.
The practice of keeping time relies on stable oscillations. In grandfather clocks, the length of a second is marked by a single swing of the pendulum. In digital watches, the vibrations of a quartz crystal mark much smaller fractions of time. And in atomic clocks, the world’s state-of-the-art timekeepers, the oscillations of a laser beam stimulate atoms to vibrate at 9.2 billion times per second. These smallest, most stable divisions of time set the timing for today’s satellite communications, GPS systems, and financial markets.
A clock’s stability depends on the noise in its environment. A slight wind can throw a pendulum’s swing out of sync. And heat can disrupt the oscillations of atoms in an atomic clock. Eliminating such environmental effects can improve a clock’s precision. But only by so much.
