Physics News and Discussions

[weatheriscool]

Experimental evidence for long-distance electrodynamic intermolecular forces
https://phys.org/news/2022-02-experimen ... cular.html
by Thamarasee Jeewandara , Phys.org

While classical and quantum electrodynamics present the existence of dipole-dipole long-range electrodynamics forces, they remain to be experimentally observed. The discovery of completely new and unanticipated forces that are present between biomolecules have considerable impact to understand the dynamics of molecular machines at work within living organisms. In a new report now published in Science Advances, Mathias Lechelon and a research team at the French National Centre for Scientific Research (CNRS) France conducted two independent experiments based on different physical effects, which they detected via fluorescence correlation spectroscopy and terahertz spectroscopy, respectively, to demonstrate experimental activation of resonant electrodynamic intermolecular forces. The outcomes provided unprecedented experimental proof-of-principle of a physical phenomenon with importance in biology. According to the study, aside from thermal fluctuations that randomly drove molecular motion, resonant and selective electrodynamic forces contributed to molecular encounters in crowded cellular spaces.

[weatheriscool]

Vacuum fluctuations break topological protection
https://phys.org/news/2022-03-vacuum-fl ... gical.html
by An­dreas Trabe­singer, ETH Zurich

A hallmark of so-called topological quantum states is that they are protected against local perturbations. ETH physicists now demonstrate that in the paradigmatic case of the integer quantum Hall effect, vacuum fluctuations can cause a breakdown of topological protection.

"Up to 1980 nobody expected that there exists an effect like the Quantized Hall Effect, which depends exclusively on fundamental constants and is not affected by irregularities in the semiconductor like impurities or interface effects." So spoke the German physicist Klaus von Klitzing on receiving the 1985 Nobel Prize in Physics. He was recognized for his discovery, in 1980, of a quantised version of the Hall effect in two-dimensional electron gasses. The unexpected robustness of the 'integer quantum Hall effect', as it has become known, in fact enabled von Klitzing's discovery in the first place. He was working with semiconductors—materials famously plagued by imperfections—yet observed an astonishingly 'clean' quantization of the Hall conductivity. The fact that such quantum systems can be so well protected against local perturbations was later explained in the framework of topological properties of electronic many-body states. But that protection can break down in unexpected ways, as the group of Prof. Jérôme Faist at the Institute of Quantum Electronics now reports. Writing in Science, they present experiments in which they established that exposing a quantum Hall system to the strongly enhanced quantum vacuum fluctuations of a tight cavity provides a novel and potentially general route to substantially modify quantum states. Such 'vacuum-field engineering' might lead to new experimental capability—but could also cause unwanted interference in experiments combining two-dimensional materials and resonators.

[caltrek]

Event Horizons are Tunable Factories of Quantum Entanglement
March 4, 2022

https://www.eurekalert.org/news-releases/945484

Introduction:

(EurekAlert) LSU physicists have leveraged quantum information theory techniques to reveal a mechanism for amplifying, or “stimulating,” the production of entanglement in the Hawking effect in a controlled manner. Furthermore, these scientists propose a protocol for testing this idea in the laboratory using artificially produced event horizons. These results have been recently published in Physical Review Letters, “Quantum aspects of stimulated Hawking radiation in an analog white-black hole pair,” where Ivan Agullo, Anthony J. Brady and Dimitrios Kranas present these ideas and apply them to optical systems containing the analog of a pair white-black hole.

Black holes are some of the most mystifying objects in our universe, largely due to the fact that their inner-workings are hidden behind a completely obscuring veil — the black hole’s event horizon.

In 1974, Stephen Hawking added more mystique to the character of black holes by showing that, once quantum effects are considered, a black hole isn’t really black at all but, instead, emits radiation, as if it was a hot body, gradually losing mass in the so-called “Hawking evaporation process.” Further, Hawking’s calculations showed that the emitted radiation is quantum mechanically entangled with the bowels of the black hole itself. This entanglement is the quantum signature of the Hawking effect. This astounding result is difficult, if not impossible, to be tested on astrophysical black holes, since the faint Hawking radiation gets overshined by other sources of radiation in the cosmos.

On the other hand, in the 1980’s, a seminal article by William Unruh established that the spontaneous production of entangled Hawking particles occurs in any system that can support an effective event horizon. Such systems generally fall under the umbrella of “analog gravity systems” and opened a window for testing Hawking's ideas in the laboratory.

Serious experimental investigations into analog gravity systems — made of Bose-Einstein condensates, non-linear optical fibers, or even flowing water — have been underway for more than a decade. Stimulated and spontaneously-generated Hawking radiation has recently been observed in several platforms, but measuring entanglement has proved elusive due to its faint and fragile character.

[weatheriscool]

Physicists show how frequencies can easily be multiplied without special circuitry
https://phys.org/news/2022-03-physicist ... uitry.html
by Martin-Luther-Universität Halle-Wittenberg

A new discovery by physicists at Martin Luther University Halle-Wittenberg (MLU) could make certain components in computers and smartphones obsolete. The team has succeeded in directly converting frequencies to higher ranges in a common magnetic material without the need for additional components. Frequency multiplication is a fundamental process in modern electronics. The team reports on its research in the latest issue of Science.

Digital technologies and devices are already responsible for about ten percent of global electricity consumption, and the trend is rising sharply. "It is therefore necessary to develop more efficient components for information processing," says Professor Georg Woltersdorf, a physicist from MLU.

Non-linear electronic circuits are typically used to generate the high-frequency gigahertz signals needed to operate today's devices. The team at MLU has now found a way to do this within a magnetic material without the electronic components that are usually used for this. Instead, the magnetization is excited by a low-frequency megahertz source. Using the newly discovered effect, the source generates several frequency components, each of which is a multiple of the excitation frequency. These cover a range of six octaves and reach up to several gigahertz. "This is like hitting the lowest note on a piano while also hearing the corresponding harmonic tones of the higher octaves," explains Woltersdorf.

[caltrek]

University of Nevada, Las Vegas Researchers Discover New Form of Ice
March 18, 2022

[url][https://www.eurekalert.org/news-releases/946973/url]

Introduction:

(EurekAlert) UNLV researchers have discovered a new form of ice, redefining the properties of water at high pressures.

Solid water, or ice, is like many other materials in that it can form different solid materials based on variable temperature and pressure conditions, like carbon forming diamond or graphite. However, water is exceptional in this aspect as there are at least 20 solid forms of ice known to us.

A team of scientists working in UNLV’s Nevada Extreme Conditions Lab pioneered a new method for measuring the properties of water under high pressure. The water sample was first squeezed between the tips of two opposite-facing diamonds—freezing into several jumbled ice crystals. The ice was then subjected to a laser-heating technique that temporarily melted it before it quickly re-formed into a powder-like collection of tiny crystals.

By incrementally raising the pressure, and periodically blasting it with the laser beam, the team observed the water ice make the transition from a known cubic phase, Ice-VII, to the newly discovered intermediate, and tetragonal, phase, Ice-VIIt, before settling into another known phase, Ice-X.

Zach Grande, a UNLV Ph.D. student, led the work which also demonstrated that the transition to Ice-X, when water stiffens aggressively, occurs at much lower pressures than previously thought.

[weatheriscool]

New experiment could confirm the fifth state of matter in the universe
https://phys.org/news/2022-03-state-universe.html
by University of Portsmouth

An experiment that could confirm the fifth state of matter in the universe—and change physics as we know it—has been published in a new paper from the University of Portsmouth.

Physicist Dr. Melvin Vopson has already published research suggesting that information has mass and that all elementary particles, the smallest known building blocks of the universe, store information about themselves, similar to the way humans have DNA.

Now, he has designed an experiment—which if proved correct—means he will have discovered that information is the fifth form of matter, alongside solid, liquid, gas and plasma.

Dr. Vopson said: "This would be a eureka moment because it would change physics as we know it and expand our understanding of the universe. But it wouldn't conflict with any of the existing laws of physics.

"It doesn't contradict quantum mechanics, electrodynamics, thermodynamics or classical mechanics. All it does is complement physics with something new and incredibly exciting."

Dr. Vopson's previous research suggests that information is the fundamental building block of the universe and has physical mass.

He even claims that information could be the elusive dark matter that makes up almost a third of the universe.

He said: "If we assume that information is physical and has mass, and that elementary particles have a DNA of information about themselves, how can we prove it? My latest paper is about putting these theories to the test so they can be taken seriously by the scientific community."

[weatheriscool]

Quantum physics sets a speed limit to electronics
https://phys.org/news/2022-03-quantum-p ... onics.html
by Vienna University of Technology

How fast can electronics be? When computer chips work with ever shorter signals and time intervals, at some point they come up against physical limits. The quantum-mechanical processes that enable the generation of electric current in a semiconductor material take a certain amount of time. This puts a limit to the speed of signal generation and signal transmission.

TU Wien (Vienna), TU Graz and the Max Planck Institute of Quantum Optics in Garching have now been able to explore these limits: The speed can definitely not be increased beyond one petahertz (one million gigahertz), even if the material is excited in an optimal way with laser pulses. This result has now been published in the scientific journal Nature Communications.

[raklian]

Gas made out of photons? That's pretty... photon-y.

[weatheriscool]

Engineering quantum states in solids using light
https://phys.org/news/2022-03-quantum-s ... olids.html
by Pohang University of Science & Technology

A POSTECH research team led by Professor Gil-Ho Lee and Gil Young Cho (Department of Physics) has developed a platform that can control the properties of solid materials with light and measure them.

Recognized for developing a platform to control and measure the properties of materials in various ways with light, the findings from the study were published in the journal Nature on March 15, 2022.

The electrical properties of a material are determined by the movement of electrons in the material. For example, a material is defined as a metal if electrons can move freely; otherwise, it is an insulator. In order to change the electrical properties of these solids, applying heat or pressure or adding impurities have been generally used. This is because the change in the position of the atoms in the solid changes the movement of electrons accordingly.

[weatheriscool]

Lottery luck in the light of physics: Researchers present theory on the dynamics of many-particle systems
https://phys.org/news/2022-03-lottery-l ... amics.html
by Bayreuth University

Physicists at the University of Bayreuth are among the international pioneers of power functional theory. This new approach makes it possible for the first time to precisely describe the dynamics of many-particle systems over time. The particles can be atoms, molecules or larger particles invisible to humans. The new theory generalizes the classical density functional theory, which only applies to many-particle systems in thermal equilibrium. In Reviews of Modern Physics, a research team led by Prof. Dr. Matthias Schmidt presents the basic features of the theory, which was significantly developed and elaborated in Bayreuth.

A many-particle system is in thermal equilibrium when the temperature in its interior is balanced and no heat flows take place. This does not necessarily mean that the system is in a rigid state of rest. Some many-particle systems can also be compared to a lottery draw machine, which rotates at a constant speed. The balls have a lot of freedom of movement in it and jump back and forth in a disorderly fashion. In a fluid many-particle system, the particles are packed considerably more densely than in the drum, which is why they constantly collide with each other at short distances and time intervals. Essential properties of such systems can be described completely and precisely with the density functional theory—provided that a thermal equilibrium of the system is given.

In the case of the lottery draw machine, this equilibrium is lost as soon as the uniform rotation gradually slows down and the chamber goes into reverse. Then the balls with the winning numbers roll onto a rail inside the chamber and are finally ejected. In order to record such processes precisely and without gaps, the power functional theory is needed: it translates the luck of the winners into the language of physics.

[weatheriscool]

Borexino gathers the first directional measurement of sub-MeV solar neutrinos using a monolithic scintillation detector
https://phys.org/news/2022-03-borexino- ... ithic.html
by Ingrid Fadelli , Phys.org

Borexino is a large-scale particle physics experiment that collected data until October 2021. Its key mission was to study low energy (sub-MeV) solar neutrinos using the Borexino detector, the world's most radio-pure liquid scintillator calorimeter, located at the Laboratori Nazionali del Gran Sasso near Aquila, in Italy.

The Borexino Collaboration, the research team conducting the experiment, recently gathered the first experimental measurement of sub-MeV solar neutrinos using a scintillation detector. This measurement, presented in a paper published in Physical Review Letters, could open new possibilities for the hybrid reconstruction of particle physics events using Cherenkov and scintillation signatures simultaneously.

"The main idea behind this work was to gather experimental proof that it is possible to use the information given by the Cherenkov photons even in a monolithic scintillation detector," Johann Martyn, one of the researchers who carried out the study, told Phys.org.

Currently, there are two main types of detectors for studying neutrinos, namely water Cherenkov detectors, such as the Super-Kamiokande (SNO) detector and liquid scintillator detectors, such as the Borexino detector. In water Cherenkov detectors, neutrinos scatter off electrons in the medium. If these electrons are moving faster than the speed of light in the water, they produce Cherenkov radiation.

[weatheriscool]

Research places new limits on the bizarre behavior of neutrinos

by Adam Becker, Lawrence Berkeley National Laboratory
https://phys.org/news/2022-04-limits-bi ... rinos.html

In a laboratory under a mountain, physicists are using crystals far colder than frozen air to study ghostly particles, hoping to learn secrets from the beginning of the universe. Researchers at the Cryogenic Underground Observatory for Rare Events (CUORE) announced this week that they had placed some of the most stringent limits yet on the strange possibility that the neutrino is its own antiparticle. Neutrinos are deeply unusual particles, so ethereal and so ubiquitous that they regularly pass through our bodies without us noticing. CUORE has spent the last three years patiently waiting to see evidence of a distinctive nuclear decay process, only possible if neutrinos and antineutrinos are the same particle. CUORE's new data shows that this decay doesn't happen for trillions of trillions of years, if it happens at all. CUORE's limits on the behavior of these tiny phantoms are a crucial part of the search for the next breakthrough in particle and nuclear physics—and the search for our own origins.

"Ultimately, we are trying to understand matter creation," said Carlo Bucci, researcher at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy and the spokesperson for CUORE. "We're looking for a process that violates a fundamental symmetry of nature," added Roger Huang, a postdoctoral researcher at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and one of the lead authors of the new study.

CUORE—Italian for "heart"—is among the most sensitive neutrino experiments in the world. The new results from CUORE are based on a data set ten times larger than any other high-resolution search, collected over the last three years. CUORE is operated by an international research collaboration, led by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy and Berkeley Lab in the US. The CUORE detector itself is located under nearly a mile of solid rock at LNGS, a facility of the INFN. U.S. Department of Energy-supported nuclear physicists play a leading scientific and technical role in this experiment. CUORE's new results were published today in Nature.

[weatheriscool]

The most precise-ever measurement of W boson mass suggests the standard model needs improvement
https://phys.org/news/2022-04-precise-e ... ndard.html
by Fermi National Accelerator Laboratory

After 10 years of careful analysis and scrutiny, scientists of the CDF collaboration at the U.S. Department of Energy's Fermi National Accelerator Laboratory announced today that they have achieved the most precise measurement to date of the mass of the W boson, one of nature's force-carrying particles. Using data collected by the Collider Detector at Fermilab, or CDF, scientists have now determined the particle's mass with a precision of 0.01%—twice as precise as the previous best measurement. It corresponds to measuring the weight of an 800-pound gorilla to 1.5 ounces.

The new precision measurement, published in the journal Science, allows scientists to test the standard model of particle physics, the theoretical framework that describes nature at its most fundamental level. The result: The new mass value shows tension with the value scientists obtain using experimental and theoretical inputs in the context of the standard model.

[weatheriscool]

Researchers engineer electrically tunable graphene devices to study rare physics
https://phys.org/news/2022-04-electrica ... -rare.html
by University of Manchester

An international team, co-led by researchers at The University of Manchester's National Graphene Institute (NGI) in the UK and the Penn State College of Engineering in the US, has developed a tunable graphene-based platform that allows for fine control over the interaction between light and matter in the terahertz (THz) spectrum to reveal rare phenomena known as exceptional points. The team published their results today in Science.

The work could advance optoelectronic technologies to better generate, control and sense light and potentially communications, according to the researchers. They demonstrated a way to control THz waves, which exist at frequencies between those of microwaves and infrared waves. The feat could contribute to the development of 'beyond-5G' wireless technology for high-speed communication networks.

Weak and strong interactions

Light and matter can couple, interacting at different levels: weakly, where they might be correlated but do not change each other's constituents; or strongly, where their interactions can fundamentally change the system. The ability to control how the coupling shifts from weak to strong and back again has been a major challenge to advancing optoelectronic devices—a challenge researchers have now solved.

"We have demonstrated a new class of optoelectronic devices using concepts of topology—a branch of mathematics studying properties of geometric objects," said co-corresponding author Coskun Kocabas, professor of 2D device materials at The University of Manchester. "Using exceptional point singularities, we show that topological concepts can be used to engineer optoelectronic devices that enable new ways to manipulate terahertz light."

[weatheriscool]

Homing in on the Higgs boson interaction with the charm quark
https://phys.org/news/2022-03-homing-hi ... charm.html
by Ana Lopes, CERN

Since the discovery of the Higgs boson a decade ago, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) have been hard at work trying to unlock the secrets of this special particle. In particular, the collaborations have been investigating in detail how the Higgs boson interacts with fundamental particles such as the particles that make up matter, quarks and leptons. In the Standard Model of particle physics, these matter particles fall into three "generations" of increasing mass, and the Higgs boson interacts with them with a strength that is proportional to their mass. Any deviation from this behavior would provide a clear indication of new phenomena.

[caltrek]

W Boson Apparently More Massive than Expected – a Physicist Explains What it Means for the Standard Model
by Jhon Conway
April 13, 2022

https://theconversation.com/a-decade-of ... del-181028

Introduction:

(The Conversation) “You can do it quickly, you can do it cheaply, or you can do it right. We did it right.” These were some of the opening remarks from David Toback, leader of the Collider Detector at Fermilab, as he announced the results of a decadelong experiment to measure the mass of a particle called the W boson.

I am a high energy particle physicist, and I am part of the team of hundreds of scientists that built and ran the Collider Detector at Fermilab in Illinois – known as CDF.

After trillions of collisions and years of data collection and number crunching, the CDF team found that the W boson has slightly more mass than expected. Though the discrepancy is tiny, the results, described in a paper published in Science on April 7, 2022, have electrified the particle physics world. If the measurement is correct, it is yet another strong signal that there are missing pieces to the physics puzzle of how the universe works.

Conclusion:

Even before this measurement, some theorists had proposed potential new particles or forces that would result in the observed deviation. In the coming months and years, I expect a raft of new papers seeking to explain the puzzling mass of W bosons.

As a particle physicist, I am confident in saying that there must be more physics waiting to be discovered beyond the Standard Model. If this new result holds up, it will be the latest in a series of findings showing that the Standard Model and real-world measurements often don’t quite match. It is these mysteries that give physicists new clues and new reasons to keep searching for fuller understanding of matter, energy, space and time.

[weatheriscool]

Observation of the branched flow of spatially incoherent light in dish soap
https://phys.org/news/2022-04-spatially ... -soap.html
by Bob Yirka , Phys.org

A team of researchers at Technion-Israel Institute of Technology has conducted the first experimental observation of the branched flow of spatially incoherent light—in this case, using liquid dish soap. In their paper published in the journal Physical Review X, the group describes their experiments involving shining light on 2D samples of liquid dish soap and their observations.

Prior research has shown that light moving through a disordered media can lead to branching, where some amount of a beam can take one path around an object while another part of the same beam can take another path. Such branching can lead to channels of light moving through a given medium. In this new effort, the researchers used liquid dish soap as the medium.

[weatheriscool]

Research team measures the mass of the top quark with unparalleled accuracy
https://phys.org/news/2022-04-team-mass ... uracy.html
by CERN

The CMS collaboration at the Large Hadron Collider (LHC) has performed the most accurate ever measurement of the mass of the top quark—the heaviest known elementary particle. The latest CMS result estimates the value of the top-quark mass with an accuracy of about 0.22%. The substantial gain in accuracy comes from new analysis methods and improved procedures to consistently and simultaneously treat different uncertainties in the measurement.

The precise knowledge of the top-quark mass is of paramount importance to understand our world at the smallest scale. Knowing this heaviest elementary particle as intimately as possible is crucial because it allows testing of the internal consistency of the mathematical description of all elementary particles, called the Standard Model.

For example, if the masses of the W boson and Higgs boson are known accurately, the top-quark mass can be predicted by the Standard Model. Likewise, using the top-quark and Higgs-boson masses, the W-boson mass can be predicted. Interestingly, despite much progress, the theoretical-physics definition of mass, which has to do with the effect of quantum-physics corrections, is still tough to pin down for the top quark.

[weatheriscool]

Lab creates superfluid circuit using fermions to study electron behavior
https://phys.org/news/2022-04-lab-super ... ctron.html
by Dartmouth College

Researchers at Dartmouth College have built the world's first superfluid circuit that uses pairs of ultracold electron-like atoms, according to a study published in Physical Review Letters.

The laboratory test bed gives physicists control over the strength of interactions between atoms, providing a new way to explore the phenomena behind exotic materials such as superconductors.

"Much of modern technology revolves around controlling the flow of electrons around circuits," said Kevin Wright, assistant professor of physics at Dartmouth and senior researcher of the study. "By using electron-like atoms we can test theories in ways that were not possible before."

While conductive materials such as copper are well understood, researchers do not completely understand how electrons move or can be controlled in exotic materials like topological insulators and superconductors that can be useful for building quantum computers.

[weatheriscool]

Scientists turn a hydrogen molecule into a quantum sensor
https://phys.org/news/2022-04-scientist ... ensor.html
by Brian Bell, University of California, Irvine

Physicists at the University of California, Irvine have demonstrated the use of a hydrogen molecule as a quantum sensor in a terahertz laser-equipped scanning tunneling microscope, a technique that can measure the chemical properties of materials at unprecedented time and spatial resolutions.

This new technique can also be applied to analysis of two-dimensional materials which have the potential to play a role in advanced energy systems, electronics and quantum computers.

Today in Science, the researchers in UCI's Department of Physics & Astronomy and Department of Chemistry describe how they positioned two bound atoms of hydrogen in between the silver tip of the STM and a sample composed of a flat copper surface arrayed with small islands of copper nitride. With pulses of the laser lasting trillionths of a second, the scientists were able to excite the hydrogen molecule and detect changes in its quantum states at cryogenic temperatures and in the ultrahigh vacuum environment of the instrument, rendering atomic-scale, time-lapsed images of the sample.

"This project represents an advance in both the measurement technique and the scientific question the approach allowed us to explore," said co-author Wilson Ho, Bren Professor of physics & astronomy and chemistry. "A quantum microscope that relies on probing the coherent superposition of states in a two-level system is much more sensitive than existing instruments that are not based on this quantum physics principle."