Single photon detectors are essential for various quantum and imaging applications. Here, the authors report graphene bolometers able to detect single near-infrared photons at temperatures up to 1.2 K with intrinsic quantum efficiency up to 87%, dark count < 1 per second and effective noise equivalent power down to 2 × 10−22 W/ $$\sqrt{{{{\rm{Hz}}}}}$$ Hz.
Different processes can produce similar spacecraft observations, making it difficult to determine how particles move through Earth’s radiation belt.
A spacecraft passing through Earth’s radiation belts can record particle behavior that looks random even when the underlying motion is highly organized. New research suggests that the limited resolution of spacecraft measurements can hide fine structures in high-energy particle populations, making predictable movement resemble diffusion.
The International Space Science Institute (ISSI) research team, led by the University of Birmingham and the Czech Academy of Science, reports in Physical Review Research that distinctly structured particle motion can produce observations nearly indistinguishable from patterns usually attributed to random scattering.
Antineutrinos from residual radioactive decay can reveal activity inside nuclear reactors even after they have been shut down.
A nuclear reactor does not become completely silent when it shuts down. Long after power production stops, radioactive, long-lived fission products continue decaying for months or years, releasing a faint stream of particles called antineutrinos. (Anti)neutrinos are the lightest and among the most elusive particles known in the Universe, passing through reactor structures and shielding with little obstruction.
The Double Chooz collaboration has now directly measured this lingering antineutrino emission for the first time. Led by Anthony Onillon and Thierry Lasserre of the Max-Planck-Institut für Kernphysik (MPIK) in Heidelberg, Germany, the research was recently published in Physical Review Letters.
MIT physicists have uncovered a surprising split in the behavior of electrons inside a quantum material: two nearly identical electronic patterns rebuild themselves in fundamentally different ways.
Electrons inside a solid do not always behave like independent particles. Under the right conditions, enormous numbers of them can reorganize together, producing entirely new states of matter with properties that the original material did not appear to possess.
MIT physicists have now watched that collective reorganization unfold in unusual detail. Their experiments reveal that two electronic phases occupying the same quantum material can form through fundamentally different mechanisms, even though both involve the same underlying type of electron order.
When certain atoms are irradiated with laser light, they can produce a very different kind of laser light: laser pulses with extremely high frequencies in the X-ray range. These laser pulses, which helped achieve record-breaking results at TU Wien in the 1990s, were the subject of the 2023 Nobel Prize in Physics.
However, the theoretical model of this effect makes a clear prediction: There is an upper limit to the energy, depending on the properties of the laser beam directed at the atoms. Above a certain value, known as the energy cutoff, hardly any X-rays are produced.
Now, however, a new experiment jointly performed by teams at TU Wien and the University of California San Diego has succeeded in overcoming this textbook cutoff rule: Using helium atoms, the researchers reached a much higher energy range than standard theory would allow. The reason lies in the interaction between the two electrons in the helium atom: They can release their energy simultaneously.
A University of Kansas physicist played a leading role in a CERN study showing that two rival explanations for how gluons behave inside atomic nuclei can now be experimentally distinguished.
The research, carried out within the ALICE experiment at CERN’s Large Hadron Collider and published in Physical Review Letters, reports the first multidimensional measurement of incoherent J/ψ (pronounced “JAY-sigh”) photonuclear production as a function of both interaction energy and momentum transfer. The measurement gives scientists their clearest view yet of how gluons, the particles that bind quarks together, are arranged inside atomic nuclei at high energies.
“Although quarks are often described as the fundamental building blocks of matter, nearly all the mass of the visible universe—from the atoms in our bodies to the matter inside stars—actually comes from the energy carried by gluons and the strong force that binds quarks together,” said nuclear physicist Daniel Tapia Takaki, professor of physics & astronomy at KU and member of the ALICE collaboration. “Understanding how gluons behave inside nuclei is therefore essential to understanding how matter itself acquires its mass and structure.”
In a new Nature Physics study, researchers accelerated electrons to more than twice the energy predicted by the traditional dephasing limit for laser-plasma accelerators operating over the same distance. This was made possible by a specially engineered laser pulse called a flying focus, which counteracts a longstanding limitation known as “dephasing.”
Laser-plasma accelerators use an intense, ultrashort laser pulse to drive a wave of charge through a plasma. In principle, this makes it possible to accelerate particles to very high energies over just centimeters, rather than kilometers.
The problem is that the accelerating plasma wave cannot keep pace with the electrons riding it. The electrons move at speeds close to the speed of light, but the laser pulse driving the wave travels slightly slower. Over distance, the electrons manage to outrun the plasma wave. This dephasing causes the electrons to stop gaining energy, thereby affecting the amount of energy such accelerators can deliver.
Skyrmions—essentially magnetic vortices—represent a promising approach in spintronics; in the future, they could serve as components in storage media or computers, potentially complementing established CMOS technologies. Researchers at Johannes Gutenberg University Mainz (JGU) have now visualized the interaction of antiferromagnetic skyrmions for the first time and shown that antiferromagnetic skyrmions move reproducibly along straight trajectories aligned with the driving electric current.
“Our results establish a quantitative framework for the interactions of antiferromagnetic skyrmions. In doing so, they pave the way for spintronic devices based on large numbers of skyrmions,” said Mona Bhukta from the research group of professor Mathias Kläui at the JGU Institute of Physics. The researchers published their findings today in the journal Nature Physics.
From schools of fish and flocks of birds to microscopic synthetic particles, many systems in nature and the laboratory consist of individual units or agents that move by consuming energy. These systems are known as active matter because their components continuously use energy to generate motion, either individually or through interactions with their environment.
Inspired by such systems, researchers have become increasingly interested in nonreciprocal interactions, in which the influence one particle exerts on another is not equally returned. In other words, one particle can affect another more strongly than it is affected in return, effectively breaking action-reaction symmetry. This is surprising because, under Newton’s third law, passive particles cannot continuously push one another in the same direction.
In this system, however, nonequilibrium electrohydrodynamic flows allow one particle to effectively “chase” another, so activity emerges even though the particles themselves are not self-propelled. Such asymmetry can generate entirely new forms of collective motion and self-organization. However, experimental realizations have largely been limited to small particle clusters.