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Category: particle physics – Page 313

Schran agrees. “This new mechanism of friction is definitely very interesting and exciting,” he says. “But what is missing in my opinion, is a clear benchmark measurement.” Quantifying, for instance, how friction changes based on water’s interaction with single versus multiple layers of carbon atoms could go a long way to fully verifying the new theory, which predicts that greater numbers of electrons in the multilayered carbon will boost friction.

The study team is already progressing along this path and dreaming of what lies beyond. They are hoping to eventually test their theory with flowing liquids other than water, and nanotubes composed of elements besides carbon. In such cases, molecules in the liquid and the electrons within nanotube walls would follow different patterns of interaction, possibly leading to changes in the degree of quantum friction. Lydéric Bocquet says that it may even be possible to control the amount of friction a flowing liquid experiences by constructing nanotubes with electron behavior explicitly in mind.

The new study sets the stage for years of complex exploration by experimental and theoretical physicists alike and, according to Kavokine, also signals a fundamental shift in how physicists should think about friction. “Physicists have long thought that it is different at the nanoscale, but this difference was not so obvious to find and describe,” he says. “They were dreaming about some quantum behavior arising at these scales—and now we have shown how it does.”

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Quanta Magazine.

In The Structure of Scientific Revolutions, the philosopher of science Thomas Kuhn observed that scientists spend long periods taking small steps. They pose and solve puzzles while collectively interpreting all data within a fixed worldview or theoretical framework, which Kuhn called a paradigm. Sooner or later, though, facts crop up that clash with the reigning paradigm. Crisis ensues. The scientists wring their hands, reexamine their assumptions and eventually make a revolutionary shift to a new paradigm, a radically different and truer understanding of nature. Then incremental progress resumes.

For several years, the particle physicists who study nature’s fundamental building blocks have been in a textbook Kuhnian crisis.

The crisis became undeniable in 2016, when, despite a major upgrade, the Large Hadron Collider in Geneva still hadn’t conjured up any of the new elementary particles that theorists had been expecting for decades. The swarm of additional particles would have solved a major puzzle about an already known one, the famed Higgs boson. The hierarchy problem, as the puzzle is called, asks why the Higgs boson is so lightweight — a hundred million billion times less massive than the highest energy scales that exist in nature. The Higgs mass seems unnaturally dialed down relative to these higher energies, as if huge numbers in the underlying equation that determines its value all miraculously cancel out.

Continue reading “Crisis in Particle Physics Forces a Rethink of What Is ‘Natural’” | >

Poli imagines using quantum gravity sensors to monitor groundwater or magma beneath volcanoes, or to help archaeologists uncover hidden tombs or other artifacts without having to dig them up (SN: 11/2/17). These devices could also help farmers check soil quality or help engineers inspect potential construction sites for unstable ground.

“There are many tools to measure gravity,” says Xuejian Wu, an atomic physicist at Rutgers University in Newark, N.J., who wasn’t involved in the study. Some devices measure how far gravity pulls down a mass hanging from a spring. Other tools use lasers to clock how fast an object tumbles down a vacuum chamber. But free-falling atoms, like those in quantum gravity sensors, are the most pristine, reliable test masses out there, Wu says. As a result, quantum sensors promise to be more accurate and stable in the long run than other gravity probes.

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Rice University lab manipulates ultracold Rydberg atoms to mimic quantum interactions.

Our spatial sense doesn’t extend beyond the familiar three dimensions, but that doesn’t stop scientists from playing with whatever lies beyond.

Rice University physicists are pushing spatial boundaries in new experiments. They’ve learned to control electrons in gigantic Rydberg atoms with such precision they can create “synthetic dimensions,” important tools for quantum simulations.

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Time crystals that persist indefinitely at room temperature could have applications in precision timekeeping.

We have all seen crystals, whether a simple grain of salt or sugar, or an elaborate and beautiful amethyst. These crystals are made of atoms or molecules repeating in a symmetrical three-dimensional pattern called a lattice, in which atoms occupy specific points in space. By forming a periodic lattice, carbon atoms in a diamond, for example, break the symmetry of the space they sit in. Physicists call this “breaking symmetry.”

Scientists have recently discovered that a similar effect can be witnessed in time. Symmetry breaking, as the name suggests, can arise only where some sort of symmetry exists. In the time domain, a cyclically changing force or energy source naturally produces a temporal pattern.

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The joint development team of Professor Shibata (the University of Tokyo), JEOL Ltd. and Monash University succeeded in directly observing an atomic magnetic field, the origin of magnets (magnetic force), for the first time in the world. The observation was conducted using the newly developed Magnetic-field-free Atomic-Resolution STEM (MARS). This team had already succeeded in observing the electric field inside atoms for the first time in 2012. However, since the magnetic fields in atoms are extremely weak compared with electric fields, the technology to observe the magnetic fields had been unexplored since the development of electron microscopes. This is an epoch-making achievement that will rewrite the history of microscope development.

Electron microscopes have the highest spatial resolution among all currently used microscopes. However, in order to achieve ultra-high resolution so that atoms can be observed directly, we have to observe the sample by placing it in an extremely strong lens . Therefore, atomic observation of magnetic materials that are strongly affected by the lens magnetic field such as magnets and steels had been impossible for many years. For this , the team succeeded in developing a lens that has a completely new structure in 2019. Using this new lens, the team realized atomic observation of magnetic materials, which is not affected by the lens magnetic field. The team’s next goal was to observe the magnetic fields of atoms, which are the origin of magnets (), and they continued technological to achieve the goal.

This time, the joint development team took on the challenge of observing the magnetic fields of iron (Fe) atoms in a hematite crystal (α-Fe2O3) by loading MARS with a newly developed high-sensitivity high-speed detector, and further using computer image processing technology. To observe the magnetic fields, they used the Differential Phase Contrast (DPC) method at atomic resolution, which is an ultrahigh-resolution local electromagnetic field measurement method using a scanning transmission electron microscope (STEM), developed by Professor Shibata et al. The results directly demonstrated that iron atoms themselves are small magnets (atomic magnet). The results also clarified the origin of (antiferromagnetism) exhibited by hematite at the atomic level.

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Using a new fabrication technique, NIMS has developed a diamond field-effect transistor (FET) with high hole mobility, which allows reduced conduction loss and higher operational speed. This new FET also exhibits normally off behavior (i.e., electric current flow through the transistor ceases when no gate voltage is applied, a feature that makes electronic devices safer). These results may facilitate the development of low-loss power conversion and high-speed communications devices.

Diamond has excellent wide bandgap semiconductor properties: its bandgap is larger than those of and gallium nitride, which are already in practical use. Diamond therefore could potentially be used to create power electronics and communications devices capable of operating more energy efficiently at higher speeds, voltages and temperatures. A number of R&D projects have previously been carried out with the aim of creating FETs using hydrogen-terminated diamonds (i.e., diamonds with their superficial carbon atoms covalently bonded with hydrogen atoms). However, these efforts have failed to fully exploit diamonds’ excellent wide bandgap semiconductor properties: the (a measure of how quickly holes can move) of these diamond-integrated transistors was only 1–10% that of the diamonds before integration.

The NIMS research team succeeded in developing a high-performance FET by using hexagonal boron nitride (h-BN) as a gate insulator instead of conventionally used oxides (e.g., alumina), and by employing a new fabrication technique capable of preventing the surface of hydrogen-terminated diamond from being exposed to air. At high hole densities, the hole mobility of this FET was five times that of conventional FETs with oxide gate insulators. FETs with high hole mobility can operate with lower electrical resistance, thereby reducing conduction loss, and can be used to develop higher speed and smaller electronic devices. The team also demonstrated normally-off operation of the FET, an important feature for power electronics applications. The new fabrication technique enabled removal of electron acceptors from the surface of the hydrogen-terminated diamond.

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Summary: A newly developed technique allows researchers to remotely active neurons with the aid of microscopic magnetic particles.

Source: UCL

Scientists at UCL have developed a new technique that uses microscopic magnetic particles to remotely activate brain cells; researchers say the discovery in rats could potentially lead to the development of a new class of non-invasive therapies for neurological disorders.

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