Mobius strip ties liquid crystal in knots to produce tomorrow's materials and photonic devices

Mobius strip ties liquid crystal in knots to produce tomorrow's materials and photonic devices
...they simulated adding a micron sized silica particle – or colloid – to the liquid crystal. This disrupts the orientation of the liquid crystal molecules.

For example, a colloid in the shape of a sphere will cause the liquid crystal molecules to align perpendicular to the surface of the sphere, a bit like a hedgehog's spikes.
Using a theoretical model, the University of Warwick scientists have taken this principle and extended it to colloids which have a knotted shape in the form a Möbius strip...


By adding these specially designed knotted particles they force the liquid crystal to take on the same structure, creating a knot in the liquid crystal...
"Recently it has been demonstrated that knots can be created in a variety of natural settings including electromagnetic fields, laser light, fluid vortices and liquid crystals.

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...

Computer simulation shows the sun's "heartbeat" is magnetic

Computer simulation shows the sun's "heartbeat" is magnetic: They ran their simulation on University of Montreal supercomputers which are connected to a larger network across the city. In so doing, they observed that though the sun as a whole experiences an 11 year cycle of solar polar reversals (as noted here on Earth by the periodic nature of observable sun spot activity), zonal magnetic field bands undergo a polarity reversal on average every 40 years.

Man-made material pushes the bounds of superconductivity (March 3, 2013)

Man-made material pushes the bounds of superconductivity (March 3, 2013): The researchers can tailor the material, which seamlessly alternates between metal and oxide layers, to achieve extraordinary superconducting properties — in particular, the ability to transport much more electrical current than non-engineered materials...

The researchers' new material is composed of 24 layers that alternate between the pnictide superconductor and a layer of the oxide strontium titanate. Creating such systems is difficult, especially when the arrangement of atoms, and chemical compatibility, of each material is very different.

Yet, layer after layer, the researchers maintained an atomically sharp interface...

The new material also has improved current-carrying capabilities. As they grew the superlattice, the researchers also added a tiny bit of oxygen to intentionally insert defects every few nanometers in the material. These defects act as pinning centers to immobilize tiny magnetic vortices that, as they grow in strength in large magnetic fields, can limit current flow through the superconductor. "If the vortices move around freely, the energy dissipates, and the superconductor is no longer lossless," says Eom. "We have engineered both vertical and planar pinning centers, because vortices created by magnetic fields can be in many different orientations."

The first controllable atom SQUID

The first controllable atom SQUID: Campbell and colleagues in the Laser Cooling and Trapping Group have long been investigating analogous behavior in toroidal Bose-Einstein condensates (BECs) – ultracold, donut-shaped ensembles of atoms that are all in the same quantum state and form a superfluid.

To create rotation, which is the superfluid counterpart to external magnetic fields in a SQUID, the team introduces a green laser beam perpendicular to and penetrating the plane of the superfluid ring, and slowly rotates the beam around the ring. (See animation.) The beam acts as a sort of optical paddle, causing the superfluid BEC atoms to rotate.

Just as a superconducting ring admits flux when the current exceeds a critical value, the ring of superfluid admits a vortex, resulting in a change in the circulation of atoms around the ring. Like everything else in the quantum world, the properties of those vortices are quantized – that is, they occur only at discrete values, and lead to quantized circulation states in the BEC. Campbell's team was able to observe and measure those quantum increments and for the first time was able to control the onset of discrete circulation states by tuning the power and rotational speed of the green laser.

Magnetic space whirlpools give Mercury a plasma shower - New Scientist - New Scientist

Magnetic space whirlpools give Mercury a plasma shower : To the list of scary things in space you can now add giant magnetic vortices. Huge swirls at the edge of Mercury's magnetosphere – where the planet's magnetic field meets the energetic charged particles of the solar wind – help shower the planet in solar plasma...

A new study of Messenger's data suggests the waves are stronger than thought – two to three times the strength of their terrestrial counterparts – and occur 10 to 30 times more frequently too.

Seeing quantum mechanics with the naked eye

Seeing quantum mechanics with the naked eye: They built microscopic cavities that tightly trap light in the vicinity of electrons within the chip, producing new particles called “polaritons” that weigh very little, encouraging them to move freely...

Injecting them in two laser spots, they found that the resulting quantum fluid spontaneously started oscillating backwards and forwards, in the process forming characteristic quantum pendulum states known to scientists, but at THz frequencies.

The resulting quantum liquid has some peculiar properties, including trying to repel itself. It can also only swirl around in fixed amounts, producing vortices laid out in regular lines. Increasing the number of laser beams creates even more complicated quantum states.

Superconductor May Hide Long-sought Secret - Science News

Superconductor May Hide Long-sought Secret - Science News: To probe the material, Yoichi Ando of Osaka University and colleagues in Japan injected current into it using a gold wire. This excited electrons at the surface, creating ripples of energy. Conventional superconductors have a dead spot in their surfaces that prevents low-energy, slow-wobbling ripples from forming. But a close look at this material revealed a sea of waves bouncing up and down both quickly and slowly.

Ando says that this pattern of ripples is “unambiguous evidence” of a type of superconductivity never seen before: topological superconductivity, in which electrons become waves molded into a complex shape that resembles the outside of a doughnut. These waves, says Ando, seem to be behaving like exotic two-dimensional particles at the surface of the material — specifically, Majorana fermions.

“This is the best evidence so far for Majorana fermions in a solid material,” says Taylor Hughes, a theoretical physicist at the University of Illinois at Urbana-Champaign.

Researchers create bizarre optical phenomena, defying the laws of reflection and refraction

Researchers create bizarre optical phenomena, defying the laws of reflection and refraction: "Using designer surfaces, we've created the effects of a fun-house mirror on a flat plane..."

Each antenna in the array is a tiny resonator that can trap the light, holding its energy for a given amount of time before releasing it. A gradient of different types of nanoscale resonators across the surface of the silicon can effectively bend the light before it even begins to propagate through the new medium...
"By incorporating a gradient of phase discontinuities across the interface, the laws of reflection and refraction become designer laws, and a panoply of new phenomena appear," says Zeno Gaburro, a visiting scholar in Capasso's group who was co-principal investigator for this work. "The reflected beam can bounce backward instead of forward. You can create negative refraction. There is a new angle of total internal reflection."

When superfluid physics creates the illusion of alien civilizations - io9

When superfluid physics creates the illusion of alien civilizations - io9: The faster the star spins, the more vortices open up in the superfluid on the surface of the star. They don't do so randomly - they form in triangular patterns. When the patterns get large enough, they form latticework on the surface of the star. Someone approaching (and compensating for the spin) would see the surface of the star pitted in a regular pattern. Someone looking at a more slow-moving star would see huge triangles made up of regularly-spaced holes floating on the star's surface. They would look like large, stable, geometric structures - seemingly too regular to be natural.

Physicists hit on mathematical description of superfluid dynamics

Physicists hit on mathematical description of superfluid dynamics: As a neutron star rotates, the superfluid on the surface behaves quite differently than a liquid would on the surface of the Earth. As the rotational speed increases the fluid opens a series of small vortices. As the vortices assemble into triangular patterns, the triangles build a lattice structure within the superfluid.
"When you reach the correct speed, you'll create one vortex in the middle," Bulgac said. "And as you increase the speed, you will increase the number of vortices. But it always occurs in steps."

Wave 'invisibility cloak' could shield coastlines - tech - 03 June 2011 - New Scientist

Wave 'invisibility cloak' could shield coastlines: Each hollow cylinder would be split vertically into quarter-circle arcs that fill up with water, and discharge it, depending on the water level surrounding them (see diagram). Although the cylinders are completely still, this constant filling and discharging is a form of oscillation and so is analogous to the electromagnetic oscillators that interfere with light waves in an invisibility cloak.

By adjusting the width of the vertical slits, the size of the cylinders, and their spacing, Hu calculates that the array could be tuned to water waves of a particular frequency so that it drains the peaks and then discharges to fill in the wave troughs - in effect dismantling those waves.

Physicists discover new way to visualize warped space and time

Physicists discover new way to visualize warped space and time: "By combining theory with computer simulations, Thorne and his colleagues at Caltech, Cornell University, and the National Institute for Theoretical Physics in South Africa have developed conceptual tools they've dubbed tendex lines and vortex lines.
Using these tools, they have discovered that black-hole collisions can produce vortex lines that form a doughnut-shaped pattern, flying away from the merged black hole like smoke rings. The researchers also found that these bundles of vortex lines—called vortexes—can spiral out of the black hole like water from a rotating sprinkler..."
On one side of the black hole, the gravitational waves from the spiraling vortexes add together with the waves from the spiraling tendexes. On the other side, the vortex and tendex waves cancel each other out. The result is a burst of waves in one direction, causing the merged hole to recoil.

Quantum Whirls - Science News

Quantum Whirls - Science News: ...His experiments involved spinning a cylinder the size of a skateboard and watching how the liquid helium sloshed inside.
Frustrated that none of the tracer particles he could buy would float, he created a new technique to freeze hydrogen, the only element lighter than helium, into a fog of ice particles. He sprinkled the hydrogen particles like snow onto the helium. They floated...
...Bewley shined a laser onto the supercold liquid with the hydrogen snow. He was shocked to see Feynman’s vortices pop into existence and bump into each other. A few days later, he and his adviser caught the whole dance on tape...
...The way that vortices snapped away from each other is similar to how Drake imagined magnetic field lines twisting in the sun...

Research elucidates the effect of disorder on magnetic vortex gyration

Research elucidates the effect of disorder on magnetic vortex gyration: In thin disks of magnetic material, the magnetization finds its ground state configuration to be a vortex; i.e., the magnetization is parallel to the edges of the disc rotating around a central core. When the magnetization is excited, the core of the vortex gyrates around the center of the disk.
Since this motion is relatively easy to measure, it has been the subject of substantial recent attention; in particular, recent measurements have studied the effect of disorder in the disk on this motion.
As described in their recent publication in Physical Review B, the CNST researchers find only small disorder-induced changes in the effective damping in vortex gyration and then only for small amplitude precession when the vortex core is pinned by the disorder potential.

Vortices get organized

Vortices get organized: Skyrmions are formed on some surfaces when the spins of the electrons—think of an arrow about which each electron rotates—collectively arrange such that they wrap around the surface of a sphere (Fig. 1). This pattern spirals in such a way that the spins on the outside point up whereas those at the core point down. This collection of spins can display many properties associated with a single particle. “A skyrmion crystal is the periodic array of these particle-like entities,” explains Tokura.

A Twisted Way To Take Pictures - Science News

A Twisted Way To Take Pictures - Science News: Electron microscopes snap images of minuscule objects by shooting a beam of electrons at a target and recording where the electrons scatter. A microscope using a vortex electron beam would work similarly, except the electron beam must first pass through a hologram that twists the beam into a helix, says McMorran. A beam that spirals offers even better resolution than a straight beam because its energy isn’t concentrated in the beam’s center, which is difficult to focus...
One intriguing application would be to use the beams to grab onto individual atoms, Herring says. Electrons in a twisted beam couple with electrons in the atoms of a material, and scientists controlling the electron microscope could use its lenses like a joystick to move the beam (and a captive atom) around.

Electric current moves magnetic vortices (w/ Video)

Electric current moves magnetic vortices (w/ Video): "In the next step, Christian Pfleiderer and his team made further measurements at the MIRA instrument of the neutron source FRM II in an attempt to determine why the lattice twisted when a current was applied. At first, the calculations of the theoreticians contradicted the results of the experiments in Garching. 'The magnetic structure twists, because the direction of the electric current is deflected extremely efficiently by quantum mechanical effects,' explains Christian Pfleiderer. When an electron flies through the magnetic vortex, the electron's spin reacts to the vortex (see animation). In this way the electric current exerts a force on the magnetic vortices, which eventually begin to flow."