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Category: particle physics

Atomic Clocks: Exquisite Sensors for More Than Just Time

Atomic clocks use the quantum energy levels of atoms to tell time more accurately and precisely than any other kind of clock. (Learn more about how atomic clocks work.)

But atomic clocks can be used for more than timekeeping. They can serve as quantum sensors. Indeed, companies already use portable atomic clocks to detect oil deposits under the ocean. As these clocks become even more accurate and precise, their sensing capabilities become increasingly powerful.

To understand how atomic clocks work as sensors, we need to know a bit about Einstein’s theory of general relativity. Relativity tells us that time ticks more slowly in stronger gravity. Here on Earth, for example, a clock ticks slightly more slowly at sea level than it would on the top of a mountain, because gravity is stronger at sea level. For similar reasons, clocks in space speed up relative to those on Earth.

Room-temperature vibrations could transform how industry makes graphene

Researchers have demonstrated a new technique for creating 2D materials that runs at room temperature and increases production rates tenfold over current methods, without using toxic solvents. Scientists led by Dr. Jason Stafford from the Department of Mechanical Engineering demonstrated the method can produce nanosheets of conductors, semiconductors and insulators, which are the building blocks of all digital devices and technologies produced today. The research is published in the journal Small.

Dr. Stafford said, “Our work shows a new way of making 2D materials that overcomes the production capacity issues of current methods, while simultaneously embedding sustainable manufacturing practices.”

2D materials are ultra-thin materials that consist of a few layers of atoms. They have unique electronic, thermal, and mechanical properties that differ significantly from their 3D counterparts, and are ideal components for next-generation electronics, energy and sensor technologies.

Machine learning offers faster, more reliable analysis of Fermi surfaces in search of spintronic materials

The search for next-generation electronic materials often starts with studying the Fermi surface, which serves as a map of a material’s electronic structure. Its shape varies with crystal structure, composition, and electronic band arrangement, directly impacting properties such as carrier density, magnetic behavior, and spin polarization. This makes it a crucial tool for understanding and engineering new materials.

The Fermi surface of a material is determined experimentally using techniques such as angle-resolved photoemission spectroscopy (ARPES). However, interpreting ARPES data requires specialized expertise, and the measurements themselves are often susceptible to noise. As experiments produce larger amounts of data, carefully reviewing every image by hand becomes time-consuming and inefficient.

Single X-ray photons reveal hidden light-matter interactions in 50-nanometer double slits

A rainbow reveals with colors what otherwise remains hidden: light is “refracted” by transparent matter, in this case water droplets. This same physical effect underlies many everyday technologies, like LCD screens and broadband connections based on fiber-optic cables. Light refraction is caused by an interaction between light and the atoms of matter. This brings the light waves slightly out of sync, so to speak. “X-ray light” is “refracted,” too. But the effect is difficult to measure here.

A miniature device now offers a novel approach: Researchers from the Universities of Göttingen and Hamburg, together with partners, have built the world’s smallest X-ray interferometer, to their knowledge. It has enabled them to precisely measure, for the first time, the refraction of X-rays confined to a few nanometers, and to deduce how they interact with atomic nuclei. The study was published in the journal Nature Photonics.

The new X-ray interferometer is based on the famous double-slit experiment, which Nobel laureate Richard Feynman said “has in it the heart of quantum mechanics.”

Synchrotron safety monitoring sheds light on dark photons

A scientist from Tokyo Metropolitan University has proposed using safety monitoring at synchrotron facilities to study the properties of dark photons, hypothetical particles proposed to explain dark matter. Calculations show that the X-ray source at these sites and a Geiger-Muller counter behind safety shielding could be used to propose limits on how strongly dark photons interact with normal photons. The experiment would not involve a dedicated facility and could run alongside other experiments.

Experimental particle physics is often a world of enormous collaborations, multinational funding, and dedicated sites and facilities, yielding groundbreaking triumphs such as the discovery of the Higgs boson.

The community has now turned its attention to the hunt for dark matter, some of which might account for the “missing” portion of mass in the known universe eluding detection by conventional means.

Aquila Booster turns a weak pulsar into a powerhouse of PeV particles

A point-like cosmic particle accelerator pumps out PeV gamma rays stronger than expected from a pulsar 50x weaker than Crab.

What makes this discovery remarkable is not just the energy, but the efficiency. This system appears to convert energy into high-speed particles far more effectively than current physics says it should.

In simple terms, astronomers may have found a cosmic particle accelerator that outperforms even their best theoretical designs.

To understand the breakthrough, it helps to know what scientists were looking at. A pulsar wind nebula forms when a dead star, called a pulsar, spins rapidly and blasts out a stream of charged particles at nearly the speed of light.

Deep under Antarctic ice, a long-predicted cosmic whisper finally breaks through in 13 strange bursts

A detector buried deep in Antarctic ice has captured the first experimental evidence of a predicted but never-before-seen phenomenon: radio pulses generated when high-energy cosmic rays slam into the ice sheet and trigger particle cascades inside it. Through results published in Physical Review Letters, astronomers of the Askaryan Radio Array (ARA) Collaboration have validated a key technique, which they hope will eventually allow them to detect some of the rarest and most energetic particles in the universe.

In 1962, Soviet physicist Gurgen Askaryan predicted that high-energy particles passing through a dense material should produce a distinctive burst of radio waves. When such a particle strikes an atom, it triggers a cascade of secondary particles that sweeps up electrons from the surrounding material, creating a negatively charged shower front that radiates at radio frequencies.

This “Askaryan radiation” was later confirmed in lab experiments and detected in air, but observing it in ice proved far more challenging. This is partly due to the difficulty of distinguishing genuine signals from the many sources of radio noise in polar environments, and partly because the simulations needed to model the effect in ice have only recently become sophisticated enough to make such rigorous analysis possible.

‘Aquila Booster’ challenges theoretical limits of particle acceleration in pulsar wind nebulae

The Large High Altitude Air Shower Observatory (LHAASO) has detected PeV (1015 eV) gamma-ray emission from a pulsar wind nebula powered by PSR J1849-0001 in the constellation Aquila, marking the discovery of a new PeVatron and posing a challenge to the classical theory of particle acceleration in pulsar wind nebulae.

This discovery is important because the calculated particle acceleration efficiency of this celestial structure approaches or even exceeds the theoretical limits allowed under ideal magnetohydrodynamic conditions.

This study, published in Nature Astronomy, was conducted by Prof. Liu Ruoyu, Dr. Wang Kai, and doctoral student Tong Chaonan from Nanjing University, Prof. Chen Songzhan and Assoc. Prof. Wang Lingyu from the Institute of High Energy Physics of the Chinese Academy of Sciences, and their collaborators.

Carbon nanotubes are closing the gap on copper conductivity

Carbon nanotubes are one technology that many observers believe hasn’t quite lived up to the extreme hype that surrounded them when they first appeared on the scene in the late 1990s. At that time, much was made of their extraordinary electrical, thermal, and mechanical properties, with predictions that they would revolutionize materials science, electronics, and daily life. But could we be closer to realizing some of that promise?

In a paper published in the journal Science, researchers describe a method for adding a chemical to carbon nanotube bundles that brings them closer to copper’s ability to conduct electricity.

Carbon nanotubes are nanoscale hollow cylinders of carbon atoms, a structure that allows electricity to flow through them with very low resistance. However, when you bundle millions of them together, as you would need for practical applications like power lines and electrical wiring, they lose some of their exceptional conductivity. Electrons move easily along individual nanotubes, but transferring charge between neighboring tubes in a bundle is much less efficient.

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