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Category: particle physics – Page 5

What happens when a quantum physicist is frustrated by the limitations of quantum mechanics when trying to study densely packed atoms? At EPFL, you get a metamaterial, an engineered material that exhibits exotic properties.

That frustrated physicist is Ph.D. student Mathieu Padlewski. In collaboration with Hervé Lissek and Romain Fleury at EPFL’s Laboratory of Wave Engineering, Padlewski has built a novel acoustic system for exploring condensed matter and their macroscopic properties, all the while circumventing the extremely sensitive nature that is inherent to . Moreover, the can be tweaked to study properties that go beyond solid-state physics. The results are published in Physical Review B.

“We’ve essentially built a playground inspired by that can be adjusted to study various systems. Our metamaterial consists of highly tunable active elements, allowing us to synthesize phenomena that extend beyond the realm of nature,” says Padlewski. “Potential applications include manipulating waves and guiding energy for telecommunications, and the setup may one day provide clues for harvesting energy from waves for instance.”

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A hidden quantum wave may keep particles moving, even when everything else freezes. Researchers discovered that phasons, a type of low-temperature quasiparticle found in crystal lattices, allow interlayer excitons to move, even at temperatures where motion is expected to stop.

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The standard model of particle physics is our best theory of the elementary particles and forces that make up our world: particles and antiparticles, such as electrons and positrons, are described as quantum fields. They interact through other force fields, such as the electromagnetic force that binds charged particles.

To understand the behavior of these quantum fields—and with that, our universe—researchers perform complex computer simulations of quantum field theories. Unfortunately, many of these calculations are too complicated for even our best supercomputers and pose great challenges for quantum computers as well, leaving many pressing questions unanswered.

Using a novel type of quantum computer, Martin Ringbauer’s experimental team at the University of Innsbruck, and the theory group led by Christine Muschik at IQC at the University of Waterloo, Canada, report in Nature Physics on how they have successfully simulated a complete quantum field theory in more than one spatial dimension.

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The heating effect of microwaves has long been used to accelerate reactions. A new experiment shows that microwaves can also excite molecules into a less reactive state.

According to Arrhenius’ law, heating increases the energy of molecules so that more of them can overcome the activation barrier and undergo a chemical reaction. One way to deliver heat is via microwave radiation. Since its early use in chemical synthesis, scientists have noticed that microwave-induced reactions often proceed differently compared with ones enhanced with oil baths and other traditional heating methods. This finding has led to ongoing speculation and debate—and even controversy—about the existence of microwave effects beyond heating [1]. Now Valentina Zhelyazkova of the Swiss Federal Institute of Technology (ETH) Zurich and her collaborators have demonstrated that microwaves can both speed up and slow down chemical reactions [2]. The discovery provides clear evidence of the nonthermal influence of microwaves on chemical processes. It also opens a path toward controlling reactions and understanding them more deeply.

In their investigation Zhelyazkova and her collaborators manipulated the rate of the gas-phase reaction between positively charged helium ions (He+) and carbon monoxide (CO) molecules: He++ CO → He + C++ O. According to so-called capture theory, the reaction’s rate depends on the rotational states of CO, whose quantized energies lie within the microwave band (Fig. 1). The experiment began with the preparation of separate supersonic beams of He atoms and CO molecules via high-pressure expansion into vacuum. The CO molecules were initially in the rotational ground state. By applying a precisely timed microwave pulse before the reaction, the researchers excited a fraction of the population to the first rotationally excited state, which is less reactive than the ground state. The fraction that was excited could be fine-tuned by changing the duration of the microwave pulse.

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University of Queensland scientists have cracked a long-standing puzzle in nuclear physics, showing that nuclear polarization, once thought to hinder experiments with muonic atoms, has a much smaller effect than expected.

This surprising result clears a major obstacle and paves the way for a new era of atomic research, offering deeper insights into the mysterious inner workings of atomic nuclei using exotic, muon-based atoms.

Breakthrough in Muonic Atom Research.

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Metals, as most know them, are good conductors of electricity. That’s because the countless electrons in a metal like gold or silver move more or less freely from one atom to the next, their motion impeded only by occasional collisions with defects in the material.

There are, however, metallic materials at odds with our conventional understanding of what it means to be a metal. In so-called “bad metals”—a technical term, explains Columbia physicist Dmitri Basov—electrons hit unexpected resistance: each other. Instead of the electrons behaving like individual balls bouncing about, they become correlated with one another, clumping up so that their need to move more collectively impedes the flow of an electrical current.

Bad metals may make for poor electrical conductors, but it turns out that they make good quantum materials. In work published on February 13 in the journal Science, Basov’s group unexpectedly observed unusual optical properties in the bad metal molybdenum oxide dichloride (MoOCl2).

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UC Riverside and its partners are exploring antiferromagnetic spintronics, a tech that could unlock lightning-fast, ultra-dense memory and smarter computing through quantum mechanics. The University of California, Riverside has been awarded nearly $4 million through the UC National Laboratory Fee

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Working at nanoscale dimensions, billionths of a meter in size, a team of scientists led by the Department of Energy’s Oak Ridge National Laboratory revealed a new way to measure high-speed fluctuations in magnetic materials. Knowledge obtained by these new measurements, published in Nano Letters, could be used to advance technologies ranging from traditional computing to the emerging field of quantum computing.

Many materials undergo phase transitions characterized by temperature-dependent stepwise changes of important fundamental properties. Understanding materials’ behavior near a critical transition temperature is key to developing new technologies that take advantage of unique physical properties. In this study, the team used a nanoscale quantum sensor to measure spin fluctuations near a phase transition in a magnetic thin film. Thin films with magnetic properties at room temperature are essential for data storage, sensors and electronic devices because their magnetic properties can be precisely controlled and manipulated.

The team used a specialized instrument called a scanning nitrogen-vacancy center microscope at the Center for Nanophase Materials Sciences, a DOE Office of Science user facility at ORNL. A nitrogen-vacancy center is an atomic-scale defect in diamond where a nitrogen atom takes the place of a carbon atom, and a neighboring carbon atom is missing, creating a special configuration of quantum spin states. In a nitrogen-vacancy center microscope, the defect reacts to static and fluctuating magnetic fields, allowing scientists to detect signals on a single spin level to examine nanoscale structures.

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In the past, events that took place in a flash were considered instantaneous. Yet modern experiments show that even when particles seem to shift in the blink of an eye, as with quantum entanglement, there are measurable intervals involved.

These findings spark questions about how electrons leave atoms or how entangled pairs form, opening avenues for precise control in various applications.

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Scientists are diving into the deep sea to study one of the universe’s biggest mysteries—quantum gravity.

Using KM3NeT, a vast underwater neutrino telescope, researchers are watching ghost-like particles that may hold the key to uniting the physics of the very large and the very small. By analyzing how neutrinos oscillate—or don’t—during their journey through space, they’re searching for subtle signs of decoherence, a possible effect of quantum gravity.

A tiny particle and a big physics puzzle.

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