Defying physics, engineers prove a magnetic field for light

Defying physics, engineers prove a magnetic field for light: When a light wave travels under normal conditions, its phase is proportional to how far it traveled, but it is unaffected by what path it has taken. Just like a magnetic field causes a current to switch direction, the researchers showed that by modulating the light with their device, they could make the phase of the light change not only as a function of distance traveled, but also by the shape of its path.
An array of such modulators would be powerful enough to create a field for light that is equivalent to the magnetic field for electrons; phases of light could be controlled arbitrarily by each of the modulators. This means that the phase of transmitted light could depend on the path it has taken from point A to point B, Lipson explained.

Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist

Quantum split: Particle this way, properties that way - physics-math - 23 July 2014 - New Scientist: In Grenoble, the Vienna team used a feeble magnetic field and a weakly interacting neutron absorber to make the weak measurements. They found that when they put the absorber in one path of the interferometer (say left), there was a discernible effect at the output. But when they put it in the right path, it had no such effect. The neutrons were travelling in one path only.

Next, the experimenters introduced a weak magnetic field near each arm of the interferometer, to interact with the spin of the neutrons. When they did this in the left path, there was no change in the interferometer's output. If they introduced the magnetic field in the right path, though, there was a change: the magnetic field had interacted with the spin. In other words, they had confirmed that the spin had chosen the path not taken by the parent neutron...

Cambridge team breaks superconductor world record

Cambridge team breaks superconductor world record: The Cambridge researchers managed to 'trap' a magnetic field with a strength of 17.6 Tesla - roughly 100 times stronger than the field generated by a typical fridge magnet - in a high temperature gadolinium barium copper oxide (GdBCO) superconductor, beating the previous record by 0.4 Tesla...

In order to hold in, or trap, the magnetic field, the researchers had to modify both the microstructure of GdBCO to increase its current carrying and thermal performance, and reinforce it with a stainless steel ring, which was used to 'shrink-wrap' the single grain samples. "This was an important step in achieving this result..."

...by engineering the bulk microstructure, the field is retained in the sample by so-called 'flux pinning centres' distributed throughout the material...

Clingy dark matter may slow the spin of corpse stars - physics-math - 23 June 2014 - New Scientist

Clingy dark matter may slow the spin of corpse stars - physics-math - 23 June 2014 - New Scientist: Their strong magnetic fields gradually slow their spin, but over the past 15 years, astronomers have noticed that many pulsars are slowing more than we would expect.

Chris Kouvaris at the University of Southern Denmark thinks a form of dark matter with a tiny electric charge may be putting on the brakes.

Physicists use magnetism simulation software to model US presidential elections

Physicists use magnetism simulation software to model US presidential elections: A team of physicists working at IFISC in Palma de Mallorca, Spain has used a computer simulation originally designed to model the transition of iron between magnetized states to create a model to do something similar for voting patterns in the United States...

What is possible though is modeling human behavior as it relates to voter patterns. One such behavior is the tendency of voters to be impacted by the opinions of others, whether those of people that live near them, or those that commute to places where they work...

Doing so revealed previously unknown correlations between regions that actually existed in the real world of vote casting and graphically illustrated the influence that voters have on one another. One striking example was the county to county variability displayed, indicating the percentage of votes going to either party—showing that the national mean changes from election to election, but not the degree of fluctuation between counties.

Physicists create synthetic magnetic monopole predicted more than 80 years ago

Physicists create synthetic magnetic monopole predicted more than 80 years ago: Hall's team adopted an innovative approach to investigating Dirac's theory, creating and identifying synthetic magnetic monopoles in an artificial magnetic field generated by a Bose-Einstein condensate, an extremely cold atomic gas tens of billionths of a degree warmer than absolute zero. The team relied upon theoretical work published by Möttönen and his student Ville Pietilä that suggested a particular sequence of changing external magnetic fields could lead to the creation of the synthetic monopole...

...the team was rewarded with photographs that confirmed the monopoles' presence at the ends of tiny quantum whirlpools within the ultracold gas...

RAMBO allows high-magnetic-field experiments on a tabletop

RAMBO allows high-magnetic-field experiments on a tabletop: "We can literally see the sample inside the magnet," Kono said. "We have direct optical access, whereas if you go to a national high magnetic field facility, you have a monster magnet, and you can only access the sample through a very long optical fiber. You cannot do any nonlinear or ultrafast optical spectroscopy...

Kono's group built the system to analyze very small, if not microscopic, samples. A sample plate sits on a long sapphire cylinder that passes through the coil's container and juts through one end of the magnet to place it directly in the center of the magnetic field.

The cylinder provides one direct window to the experiment; a port on the other side of the container looks directly down upon the sample. The coil is bathed in liquid nitrogen to keep it cool at around 80 kelvins (-315 degrees Fahrenheit). The sample temperature can be independently controlled from about 10 K to room temperature by adjusting the flow of liquid helium to the sapphire cylinder.

Physicists Net Fractal Butterfly: Scientific American

Physicists Net Fractal Butterfly: Scientific American: ...the pattern describes the behavior of electrons in extreme magnetic fields...

...It was known at the time that electrons under the influence of a magnetic field would race around in circles. But Hofstadter found that in theory, if the electrons were confined inside a crystalline atomic lattice, their motion would become complicated. As the magnetic field was cranked up, the energy levels that define the motion of electrons would split again and again. When represented on a graph, those energy levels revealed a pattern that looked like a butterfly — and continued to do so, even when zoomed in to infinitely small scales...

 In May, researchers reported that they had stacked a single sheet of graphene, in which carbon atoms are arranged like a honeycomb, on top of a sheet of honeycombed boron nitride. The layers create a repeating pattern that provides a larger target for magnetic fields than the hexagons in each material — effectively magnifying the field.

New evidence to aid search for charge 'stripes' in superconductors

New evidence to aid search for charge 'stripes' in superconductors: ...uncovering the detailed relationship between these stripe patterns and the appearance or disappearance of superconductivity is extremely difficult, particularly because the stripes that may accompany superconductivity are very likely moving, or fluctuating.


The scientists ground up crystals of the test material into a fine powder and placed samples of it in line with a beam of neutrons...


With increasing temperature, the scientists found that while the aspect ratio of the crystal structure changed, the displacements from average structure persisted, leading them to conclude by inference that the striped pattern of charge density also remained, even though it was no longer static.

"This is the first powder diffraction scattering evidence for fluctuating charge stripes above the temperature where we see static order..."

Magnetic charge crystals imaged in artificial spin ice

Magnetic charge crystals imaged in artificial spin ice: In the honeycomb pattern, where three magnetic poles intersect, a net charge of north or south is forced at each vertex. The magnetic "monopole charge" at each vertex influences the magnetic "charge" of the surrounding vertices. The team was able to image the crystalline structure of the magnetic charges using magnetic force microscopy...

The research team's new annealing protocol—heating the material to a high temperature where their magnetic polarity is suppressed (here, about 550 degrees Celsius)—allows the nanomagnets to flip their polarity and freely interact. As the material cools, the nanomagnets are ordered according to the interactions of their poles at the vertices...

"This work demonstrates a direction in condensed matter physics that is quite opposite to what has been done in the last sixty years or so," said Nisoli. "Instead of imagining an emergent theoretical description to model the behavior of a nature-given material and validating it indirectly, we engineer materials of desired emergent properties that can be visualized directly."

Physicist proves impossibility of quantum time crystals

Physicist proves impossibility of quantum time crystals: Bruno explains that this proof should not come as a surprise, since a 1964 theory by another Nobel Laureate, Walter Kohn, shows that an insulator is completely insensitive to a magnetic flux. Since quantum time crystals are modeled as ring-shaped Wigner crystals, and Wigner crystals are insulators, attempting to show that a magnetic flux can cause such a system to rotate is, as Bruno writes, "a hopelessly doomed endeavor."

Twisted Magnetic Fields Tie Information in a Knot: Scientific American

Twisted Magnetic Fields Tie Information in a Knot: Scientific American: Writing in Science, von Bergmann and her collaborators describe how they created skyrmions on a thin magnetic film of palladium and iron on an iridium crystal. They began with a sample in which all the atomic bar magnets were aligned. The team then used the tip of a scanning tunnelling microscope to apply a small current made up of electrons that had their spins aligned, or polarized, in a particular way. The polarized current interacted with the atomic bar magnets to twist them into knot-like configurations of skyrmions, each a few nanometers, or about 300 atoms, in diameter, says von Bergmann. The scientists could also use the polarized current to erase the knot, deleting the skyrmion...

...this is the first time that scientists have created and deleted individual magnetic skyrmions...

Super-accurate atomic clock doubles up as quantum sim - physics-math - 08 August 2013 - New Scientist

Super-accurate atomic clock doubles up as quantum sim - physics-math - 08 August 2013 - New Scientist: Electrons' behaviour inside solids can be physically modelled using networks of atoms cooled to trillionths of a degree above absolute zero...

...she and her colleagues have stumbled upon a way to mimic quantum behaviour in a system several orders of magnitude warmer: an atomic clock...

Rey says that the strontium atoms in the ground state can be used to simulate spin-down electrons, and the excited atoms, spin-up electrons. Tracking the emergence and details of the interactions between the atoms could then shed light on the nature of the quantum interactions between electrons in magnets.

Physicists freeze motion of light for a minute

Physicists freeze motion of light for a minute: To stop the light, the physicists used a glass-like crystal that contains a low concentration of ions – electrically charged atoms – of the element praseodymium. The experimental setup also includes two laser beams. One is part of the deceleration unit, while the other is to be stopped. The first light beam, called the "control beam", changes the optical properties of the crystal: the ions then change the speed of light to a high degree. The second beam, the one to be stopped, now comes into contact with this new medium of crystal and laser light and is slowed down within it. When the physicists switch off the control beam at the same moment that the other beam is within the crystal, the decelerated beam comes to a stop.


More precisely, the light turns into a kind of wave trapped in the crystal lattice. This can be explained in greatly simplified form as follows. The praseodymium ions are orbited by electrons. These behave similarly to a chain of magnets: if you put one into motion, the movement – mediated by magnetic forces – propagates in the chain like a wave. Since physicists call the magnetism of electrons "spin", a "spin wave" forms in the same manner when freezing the laser beam. This is a reflection of the laser's light wave. In this way, the Darmstadt researchers were able to store images, such as a striped pattern, made of laser light within the crystal. The information can be read out again by turning the control laser beam on again.

The Hunt for the Magnetic Monopole - IEEE Spectrum

The Hunt for the Magnetic Monopole - IEEE Spectrum: The team proposed looking for these trapped monopoles at temperatures close to absolute zero in spin ice, a peculiar class of materials with ions arranged in four-sided pyramids called tetrahedra. These tetrahedra are stacked together to make a crystal called a pyrochlore.

The atoms at each corner of the pyramids in a pyrochlore are magnetic dipoles. Just like a bar magnet, they have a magnetic field that emerges from one side (what physicists tend to call “north” by convention) and curves around the atom so that it eventually enters the opposite end (“south”)....

When the temperature of the crystalline material is relatively high, the forces that try to align the spins are easily overwhelmed by thermal fluctuations. The spins are oriented at random and can easily change direction. When the material is cooled to just a few degrees above absolute zero, the forces between spins begin to dominate...

In the case where ice rules are obeyed, the two north poles and two south poles cancel each other out. But here’s where it gets interesting: When the ice rules are not obeyed—if, for example, there are three spins pointing inward and one pointing outward—then the three north poles and one south pole in the center will give rise to a single, north magnetic pole.

What We Can Learn From the Quantum Calculations of Birds and Bacteria - Wired Science

What We Can Learn From the Quantum Calculations of Birds and Bacteria - Wired Science: We can now show that a single electronic excitation acting as a probability amplitude wave can simultaneously sample the various molecular paths connecting the antenna cells to the reaction center. The excitation effectively “picks” the most efficient route from leaf surface to sugar conversion site from a quantum menu of possible paths. This requires that all possible states of the traveling particle be superposed in a single, coherent quantum state for tens of femtoseconds.

We have seen this remarkable phenomenon in the green sulphur bacteria, but humans have not yet figured out how it is that nature can stabilize a coherent electronic quantum state in such complex systems for such long periods of time...

Remarkably, it seems that these photosynthesizing bacteria can actually use decoherence to speed up the transfer of electronic information by accessing vibrational energies in the protein bath surrounding the biological-quantum wire without losing the integrity of the information...

It seems that quantum mechanical processes in the avian eye send signals to the brain that are sensitively dependent on the angle of change in magnetic field inclination, thereby allowing the bird to map routes. The hypothesis is that pairs of light-absorbing molecules in the bird retina produce quantum mechanically entangled electrons whose quantum mechanical state depends on the angular inclination of the field and which catalyze chemical reactions that send differently valued signals to the brain depending upon the degree of inclination.

Physicists discover theoretical possibility of large, hollow magnetic cage molecules

Physicists discover theoretical possibility of large, hollow magnetic cage molecules: Although some hollow cage structures have been found, none of them is magnetic. Magnetic properties of the structure are of particular interest because a hollow magnetic structure carrying an embedded atom or molecule can be guided by an external magnetic field and may serve as an effective vehicle for targeted drug delivery.
In a new study... two VCU scientists employing state-of-the-art theoretical methods show that magnetic hollow cages larger than the original C60 fullerene that carry giant magnetic moments are possible...


According to Jena, the pair of VCU researchers demonstrated the magnetic moment of the molecule by focusing on hetero-atomic clusters consisting of transition metal atoms such as cobalt (Co) and manganese (Mn) and carbon (C) atoms. In particular, Co12C6, Mn12C6, and Mn24C18 clusters consisting of 12 cobalt and six carbon atoms, 12 manganese and six carbon atoms, and 24 manganese and 18 carbon atoms, respectively, carry magnetic moments as large as 14, 38 and 70 Bohr magnetons. In comparison, the magnetic moment of an iron (Fe) atom in crystalline iron is 2.2 Bohr magnetons.

Muscles act as metamaterials due to collective behavior, physicists show

Muscles act as metamaterials due to collective behavior, physicists show: Upon further search for possible mechanisms of negative stiffness, scientists in a new study have found that biological muscles exhibit a mechanical response that also qualifies them as metamaterials: when a tetanized (maximally contracted) muscle is suddenly extended, it comes loose, and if it is suddenly shortened, it tightens up...

Quite surprisingly, the cooperation at the nanoscale in muscles was found to be similar to magnetism; moreover, the critical point at which muscles seem finely tuned to perform near is, in this case, a direct analog of the ferromagnetic Curie point.

Penetrating the quantum nature of magnetism

Penetrating the quantum nature of magnetism: he LQM scientists, led by Henrik M. Rønnow, cooled down a copper sulfate crystal close to absolute zero (about 0.01 K) to turn it into a quantum spin liquid and then used inelastic neutron scattering to investigate the motion of electrons' spins. The experiments reveal that the magnetic properties of copper sulfate can no longer be described by the individual behavior of the magnetic moments carried by each individual electron in the sample. Instead, flipping the magnetic moment of one single electron creates two spatially separated quantum objects called spinons.

Giant, Heavy and Hollow: Physicists Create Extreme Atoms

Giant, Heavy and Hollow: Physicists Create Extreme Atoms: “If you tune your X-rays properly, you can pick which shell you want to empty out first,” says Young. “Being able to control the inner-shell dynamics is very cool.” The current record for this kind of atom-hollowing was reported last November by a group at the Center for Free-electron Laser Science in Hamburg, Germany, which used the SLAC laser to strip away, from the inside out, the 36 inner electrons of a 54-electron-strong xenon atom...

In 2008, researchers led by Dunning reported that they had managed to squeeze the normally spread-out electron into a tight packet that briefly orbited the nucleus. Last year, they added radio waves that enabled that motion to be maintained indefinitely. “It only took a century, but we recreated Bohr's atom,” says Dunning proudly...

By 2002, two collaborations had been able to make as many as 50,000 atoms of antihydrogen, but the atoms quickly annihilated on the walls of their container. It took until 2010 before researchers at ALPHA showed how to trap the atoms using three magnets with a combined field sufficient to restrain antihydrogen, with its tiny magnetic moment. At that time, the antimatter was held for just 170 milliseconds, and only about one atom was trapped for every eight times the group ran the 20–30 minute experiment, says Hangst. But the team has improved its equipment to trap one atom per experiment, and hold it for about 1,000 seconds...