A black hole in a bath: Big physics on a bench-top - physics-math - 10 March 2014 - New Scientist

A black hole in a bath: Big physics on a bench-top - physics-math - 10 March 2014 - New Scientist

Supersymmetry...  One of its central predictions is that there should be more than one Higgs particle... they might have found some clue as to where those extra particles might be – in superfluid helium-3... The discovered Higgs weighs in at around 125 gigaelectronvolts (GeV). Studying the spectrum of excitations in the superfluid helium suggests Higgs particles should also exist at energies of 210 GeV and 325 GeV. These possibilities are not excluded by results collected so far at the LHC...

By concentrating laser light into a very small spot within a waveguide made of a glass block, he can temporarily change the refractive index of the glass so that it slows down subsequent laser pulses and ultimately repels them. "What makes these analogue experiments so powerful is that from a photon or a water wave's perspective, it has no way of distinguishing whether it is crossing the event horizon of a real black hole or is in a waveguide under some weird constraints," he says.

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...

A new topological insulator breaks symmetry, and that's a good thing

A new topological insulator breaks symmetry, and that's a good thing: Most topological insulators operate as either a p-type or n-type material on both top and bottom surfaces. But BiTeCl is asymmetric: p-type on its top surface and n-type on its bottom. This means the edges of the material could function as p-n junctions – or even many microscopic p-n junctions layered on top of each other. Even better, when the material is placed in a magnetic field, these p-n junctions develop unique edge channels that can conduct electricity with zero resistance, Chen said – and this opens all sorts of possibilities.

Moreover, this unique type of material can demonstrate many other phenomena. For instance, placing it in a static electric field can induce useful magnetic properties in the material, a phenomenon known as the topological magneto-electric effect, first predicted by theorist Shoucheng Zhang of the Stanford Institute for Materials and Energy Sciences and his group. You could even use an electric charge to induce magnetic monopoles – theorized magnets that have just one pole, north or south, rather than the usual two – and then use this exotic magnetic state to do practical work, such as storing information on a hard drive, Chen said. "This is very bizarre," he said, "because people have never found magnetic monopoles as fundamental particles."

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."

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.

Artificial magnetic monopoles discovered

Artificial magnetic monopoles discovered: What happens, however, within the materials? Measurements taken by the group working under the direction of Prof. Pfleiderer in Munich using neutron scattering suggest that similar processes occur there, but individual whirls were not observed in this manner. For this reason, Stefan Buhrandt and Christoph Schütte working in Prof. Rosch's group at the University of Cologne conducted computer simulations. These showed that the whirls neighbouring the merging process observed on the surface in the experiment also occur within the materials...


Due to the fact that every whirl carries an artificial magnetic field, their creation or destruction occurs at the point of merging. "This means that an artificial magnetic monopole has to sit on this point," describes Prof. Rosch, "whenever two magnetic whirls merge in the experiment, an artificial magnetic monopole has flown through surface."

Freezing magnetic monopoles: How dipoles become monopoles and vice versa

Freezing magnetic monopoles: How dipoles become monopoles and vice versa: "Steady flows of magnetic monopoles are apparently impossible," Powell said, "but transient currents have been demonstrated, and one could imagine creating an alternating current, the magnetic equivalent of AC electricity..."

Normally all magnetic poles should be confined within two-pole couplets---the traditional magnetic dipole. However, at a low enough temperature, around 5 K, "frustration" among the magnetic atoms---they want to align with each other but can't because of the inherent geometry of the material---leads to a disordered state with strong, synchronized fluctuations. Unpaired magnetic poles can form amid this tumult. That is, particles (quasiparticle excitations, to be exact) in spin ice with a net magnetic "charge" can exist and move about. A gas of electric charges is called a "plasma," so some scientists refer to the analogous tenuous cloud of magnetic charges as a "monopole plasma."
Stephen Powell's paper, published presently in the journal Physical Review Letters, explores what happens when the fluctuations are frozen by, for example, still-colder temperatures or a high-strength magnetic field. He shows how the monopoles are confined into magnetically neutral dipoles again. He is the first to prescribe the phase transition from the monopole phase (also called the Coulomb phase since the monopoles feel the same inverse-square force effect as electric charges) into the pole-confined phase.

'Magnetricity' Behaves Like Electricity - Science News

'Magnetricity' Behaves Like Electricity - Science News: In 2009 Steven Bramwell of the University College of London found that sometimes a molecule squirms and flips. Two poles, a north and a south, are born. The molecule itself stays put, but these ghostly poles, which aren’t actually attached to a physical object, can move around independently of each other as chain reactions of flipping molecules carry them from pyramid to pyramid.
“Eventually they get so far apart that they lose all memory of each other,” says Bramwell. “The dipole splits in half and becomes two monopoles.”

Scientists create highly ordered artificial spin ice using nanotechnology

Scientists create highly ordered artificial spin ice using nanotechnology: "Artificial spin ice is built using nanotechnology and is made up of millions of tiny magnets, each thousands of times smaller than a grain of sand. The magnets exist in a lattice in what is known as a 'frustrated' structure. Like water ice, the geometry of the structure means that all of the interactions between the atoms cannot be satisfied at the same time."

Magnetic monopole deficit hints that hunt is futile - New Scientist - New Scientist

Magnetic monopole deficit hints that hunt is futile: Unlike electric charges, which abound as individual positives and negatives, magnets seem always to have both a north and south end. Yet monopoles pop up in descriptions of the early universe and also help to explain why electric charges come in discrete "quanta". If monopoles actually exist, will we ever spot one?

Our best hope may be to capture a relic monopole from the early universe, but the likelihood of this depends on how many there are near us. The limit on the number of such high-speed relic monopoles that could inhabit the Milky Way without sapping its magnetic field is called the "Parker bound".

Now readings from ANITA, a balloon-borne neutrino telescope based in Antarctica that can also detect monopoles, suggest that the maximum is just 1/10,000th of the Parker bound for monopoles moving close to the speed of light, says David Besson at the University of Kansas, Lawrence, and colleagues.

Hot on the trails of the mysterious monopole - physics-math - 04 September 2009 - New Scientist

Hot on the trails of the mysterious monopole: "Spin ice is a kind of crystalline material with essentially the same atomic arrangements as water ice. Last year, researchers demonstrated that certain states of spin ice would create monopoles that rove about the crystal. The monopoles would be seen as disturbances moving through the spins of atoms within the crystal.  Now two separate groups claim to have seen just that."