A scientific breakthrough on the tiniest scale could soon help us answer the universe’s greatest mysteries.
Kamiokande-II saw the first supernova neutrinos from the famous SN 1987A.
Every few seconds, somewhere in the observable Universe, a massive star collapses and unleashes a supernova explosion. Japan’s Super-Kamiokande observatory might now be collecting a steady trickle of neutrinos from those cataclysms, physicists say — amounting to a few detections a year.
These tiny subatomic particles are central to understanding what goes on inside a supernova: because they zip out of the star’s collapsing core and across space, they can provide information about any potentially new physics that occur under extreme conditions.
Continue reading “Huge neutrino detector sees first hints of particles from exploding stars” »
Scientists have developed a new way to trap small particles with light. Building on the Nobel Prize winning technique of optical tweezers (Arthur Ashkin, 2018), a team of physicists, led by Dr. David Phillips at the University of Exeter, has advanced the possibilities of optical trapping.
The research paper, published in the journal Science Advances, is titled “Photon-efficient optical tweezers via wavefront shaping.”
Conventional optical tweezers, developed in the 1980s, are a tightly focused laser beam which can attract and trap certain micro-sized particles or organisms, akin to grabbing something with a pair of tweezers.
A levitating microparticle is observed to recoil when a nucleus embedded in the particle decays—opening the door to future searches of invisible decay products.
For centuries, physicists have exploited momentum conservation as a powerful means to analyze dynamical processes, from billiard-ball collisions to galaxy formation to subatomic particle creation in accelerators. David Moore and his research team at Yale University have now put this approach to work in a new setting: they used momentum conservation to determine when a radioactive atom emitted a single helium nucleus, known as an alpha particle (Fig. 1) [1]. The demonstration suggests that—with further improvements—researchers might be able to use this technique to detect other nuclear-decay products, such as neutrinos and hypothetical dark-matter particles (see also Special Feature: Sensing a Nuclear Kick on a Speck of Dust).
The basic idea is simple: if the radioactive atom is embedded in a larger object, then an outgoing decay product will exert a backreaction on that object, causing it to recoil in the opposite direction. But is it really possible to detect the recoil kick from a particle as small as a helium nucleus? The answer lies in how precisely we can measure the larger object’s momentum. One of the main limitations is friction: if the larger object is slowed down by frictional forces, then its motion won’t reflect the impulse from the decaying particle.
In this work, we show that the flexible programming of the exchange-biased magnetic heterostructure enables the direct generation of various structured terahertz beams with complex polarization distributions. In the above demonstrations, we did not perform amplitude design on ENF(r), as lasers with Gaussian profiles were utilized to excite various programmed emitters. To exert control over local NF amplitudes, spatial light modulators can be further employed to manipulate the amplitude profiles of excitation lasers.
It is important to acknowledge that, owing to the inherent capability of generating only linearly polarized ENF locally, a crucial constraint arises: the NF terahertz amplitudes for the LCP and RCP components must be equal at all locations, leading to \({A}_{NF}^{L}(\mathbf{r})={A}_{NF}^{R}(\mathbf{r})\) at the emitter’s surface. As a consequence, both LCP and RCP terahertz fields are simultaneously generated in the far field. In situations where terahertz beams with a pure polarization state are of interest, one can strategically design the magnetization pattern so that desired polarization state is focused at the center, while surrounding it with other polarizations. By employing simple spatial filtering, this pure polarization state can be isolated and utilized. This concept was demonstrated by the LCP Gaussian beam in the last demonstration, where different spatial phase gradients were applied on the LCP and RCP light beams, allowing for their spatial separation in the far field.
Furthermore, by fabricating the heterostructures into appropriately oriented micro-structures, one can induce confinements onto the local charge currents [38,39,40]. This enables independent control over the x- and y-components of the local terahertz fields, potentially facilitating the realization of an arbitrary terahertz wave generator.
Researchers from the University of Twente in the Netherlands have gained important insights into photons, the elementary particles that make up light. They ‘behave’ in an amazingly greater variety than electrons surrounding atoms, while also being much easier to control.
These new insights have broad applications from smart LED lighting to new photonic bits of information controlled with quantum circuits, to sensitive nanosensors. Their results are published in Physical Review B.
In atoms, minuscule elementary particles called electrons occupy regions around the nucleus in shapes called orbitals. These orbitals give the probability of finding an electron in a particular region of space. Quantum mechanics determines the shape and energy of these orbitals. Similarly to electrons, researchers describe the region of space where a photon is most likely found with orbitals too.
In 1968, deep underground in the Homestake gold mine in South Dakota, Ray Davis Jr.
At the same time, Steven Weinberg and Abdus Salam were carrying out major construction work on what would become the Standard Model of particle physics, building the Higgs mechanism into Sheldon Glashow’s unification of the electromagnetic and weak interactions. The Standard Model is still bulletproof today, with one proven exception: the nonzero neutrino masses for which Davis’s observations were in hindsight the first experimental evidence.
Today, neutrinos are still one of the most promising windows into physics beyond the Standard Model, with the potential to impact many open questions in fundamental science ( CERN Courier May/June 2024 p29). One of the most ambitious experiments to study them is currently taking shape in the same gold mine as Davis’s experiment more than half a century before.
New research introduces a non-thermal method for magnetization using circularly polarized XUV light, which induces significant magnetization changes through the inverse Faraday effect, potentially transforming ultrafast data storage and spintronics.
Intense laser pulses can be used to manipulate or even switch the magnetization orientation of a material on extremely short time scales. Typically, such effects are thermally induced, as the absorbed laser energy heats up the material very rapidly, causing an ultrafast perturbation of the magnetic order.
Scientists from the Max Born Institute (MBI), in collaboration with an international team of researchers, have now demonstrated an effective non-thermal approach of generating large magnetization changes. By exposing a ferrimagnetic iron-gadolinium alloy to circularly polarized pulses of extreme ultraviolet (XUV) radiation, they could reveal a particularly strong magnetic response depending on the handedness of the incoming XUV light burst (left-or right-circular polarization).
Scientists spent ages mocking panpsychism. Now, some are warming to the idea that plants, cells, and even atoms are conscious.
The ionization energy is the amount of energy required to remove a single electron from an atom. If the atom has more than one electron, each one requires more energy than the previous one. The result is a series of increasing energy levels, and in the quantum world these energies correspond to frequencies, as in a musical scale.
This raises an interesting question: if we could hear these frequencies how would they sound? I created an app to find out, and in this video I used my app to share what I learned. As it turns out, the results are quite musical.
Continue reading “Stanley Jordan Plays the Periodical Table (Ionization Energies)” »
