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.

Study helps unlock mystery of high-temp superconductors

Study helps unlock mystery of high-temp superconductors: "Evidence has been accumulating that this phase supports an exotic density wave state that may be key to its existence...". A density wave forms in a metal if the fluid electrons themselves crystalize.
Using a scanning tunneling microscope (STM) to visualize the electronic structure of the oxygen sites within a superconductor, the team found a density wave with a d-orbital structure. (The electron density near each copper atom looks a bit like a daisy in the crystallized pattern.) That's especially surprising because most density waves have an s-orbital structure; their electron density is isotropic. "It's not the pattern you would expect," Lawler says.
In this research, Lawler and his colleagues focused on a member of the cuprate class of superconductors called bismuth strontium calcium copper oxide (BSCCO). "We now believe these density waves exist in all cuprates," says Lawler, a theorist whose contribution to the research involved subtle uses of the Fourier transform, a mathematical analysis that's useful when examining amplitude patterns in waves.

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI: The researchers used a combination of subpicosecond laser pulses and unique nanostructures to produce acoustic phonons... at a frequency of 10 gigahertz (10 billion cycles per second).

By comparison, medical ultrasounds devices today typically reach a frequency of only about 20 megahertz...

“To generate 10 GHz acoustic frequencies in our plasmonic nanostructures we use a technique known as picosecond ultrasonics,” said author are Kevin O’Brien. “Sub-picosecond pulses of laser light excite plasmons which dissipate their energy as heat. The nanostructure rapidly expands and generates coherent acoustic phonons. This process transduces photons from the laser into coherent phonons.”

New ‘switch’ could power quantum computing | MIT News Office

New ‘switch’ could power quantum computing | MIT News Office:  “We have demonstrated basically an atom can switch the phase of a photon. And the photon can switch the phase of an atom...”

In this case, the researchers used a laser to place a rubidium atom very close to the surface of a photonic crystal cavity, a structure of light. The atoms were placed no more than 100 or 200 nanometers — less than a wavelength of light — from the edge of the cavity. At such small distances, there is a strong attractive force between the atom and the surface of the light field, which the researchers used to trap the atom in place...

“In some sense, it was a big surprise how simple this solution was compared to the different techniques you might envision of getting the atoms there,” Vuletić says.

A grand unified theory of exotic superconductivity?

A grand unified theory of exotic superconductivity?: In the current paper, Davis and Lee propose and demonstrate within a simple model that antiferromagnetic electron interactions can drive both superconductivity and the various intertwined phases across different families of high-Tc superconductors. These intertwined phases and the emergence of superconductivity, they say, can be explained by how the antiferromagnetic influence interacts with another variable in their theoretical description, namely the "Fermi surface topology..."


"The basic assumption of our theory is that when we rip away all the complicated intertwined phases, underneath there is an ordinary metal," said Lee. "It is the antiferromagnetic interactions in this metal that make the electrons want to form the various states. The complex behavior originates from the system fluctuating from one state to another, e.g., from superconductor to charge density waves to nematic order. It is the antiferromagnetic interaction acting on the underlying simple metal that causes all the complexity."

New material gives visible light an infinite wavelength

New material gives visible light an infinite wavelength: The way light travels through matter is dependent on the material permittivity: the resistance of a material against the electric fields of light waves. Because the permittivity of silver is negative and that of silicon nitride is positive, the combined material has a permittivity which is effectively equal to zero. Therefore, it seems that the light experiences zero resistance, and propagates with an infinite phase velocity. The wavelength of the light is nearly infinite.

World's First Quantum Metamaterial Unveiled | MIT Technology Review

World's First Quantum Metamaterial Unveiled | MIT Technology Review: the split-ring resonators introduced losses because of their internal resistance...

a solution to this problem: use superconducting resonators...

The problem in the past is that physicists had arranged the circuits in series so that the combined state must be a superposition of the states of all the circuits. So if a single circuit was out of kilter, the entire experiment failed.

Macha and co got around this by embedding the quantum circuits inside a microwave resonator–a chamber about a wavelength long in which the microwaves become trapped.

To interact with a photon, each quantum circuit need only couple with the resonator itself and its nearest neighbours.

Researchers slow light to a crawl in liquid crystal matrix

Researchers slow light to a crawl in liquid crystal matrix: The new approach... uses little power, does not require an external electrical field, and operates at room temperature, making it more practical than many other slow light experiments...


The key to achieving a significant drop-off in speed is to take advantage of the fact that when light travels as a pulse it is really a collection of waves, each having a slightly different frequency, says Bortolozzo. However, all the waves in the pulse must travel together. Scientists can design materials to be like obstacles courses that "trip up" some of the waves more than others. In order to exit the material together, the pulse must wait until it can reconstitute itself...


They added a chemical component that twisted the liquid crystal molecules into a helical shape and then added dye molecules that nestled in the helical structures. The dye molecules change their shape when irradiated by light, altering the optical properties of the material and hence changing the relative velocities of the different wave components of the light pulse as it travelled through. In addition, the helical structure of the liquid crystal matrix ensures a long lifetime of the shape-shifted dyes, which makes it possible to "store" a light pulse in the medium and later release it on demand...

Bizarre Liquid More Stable Than Solid Crystal | LiveScience

Bizarre Liquid More Stable Than Solid Crystal | LiveScience: "When we make the bonds more flexible, the liquid phase remains stable even at extremely low temperatures," Smallenburg said. "The particles will simply never order into a crystal, unless they are compressed to high densities." �

What does mercury being liquid at room temperature have to do with Einstein’s theory of relativity? | The Curious Wavefunction, Scientific American Blog Network

What does mercury being liquid at room temperature have to do with Einstein’s theory of relativity? | The Curious Wavefunction, Scientific American Blog Network:  From Niels Bohr’s theory of atomic structure we know that the velocity of an electron is proportional to the atomic number of an element. For light elements like hydrogen (atomic number 1) the velocity is insignificant compared to the speed of light so relativity can be essentially ignored. But for the 1s electron of mercury (atomic number 80) this effect becomes significant; the electron approaches about 58% of the speed of light, and its mass increases to 1.23 times its rest mass. Relativity has kicked in. Since the radius of an electron orbit in the Bohr theory (orbital to be precise) goes inversely as the mass, this mass increase results in a 23% decrease in the orbital radius. This shrinkage makes a world of difference since it results in stronger attraction between the nucleus and the electrons, and this effect translates to the outermost 6s orbital as well as to other orbitals. The effect is compounded by the more diffuse d and f orbitals insufficiently shielding the s electrons. Combined with the filled nature of the 6s orbital, the relativistic shrinkage makes mercury very reluctant indeed to share its outermost electrons and form strong bonds with other mercury atoms.

The bonding between mercury atoms in small clusters thus mainly results from weak Van der Waals forces which arise from local charge fluctuations in neighboring atoms rather than the sharing of electrons.

New phase of water could dominate the interiors of Uranus and Neptune

New phase of water could dominate the interiors of Uranus and Neptune: One lesser known phase of water is the superionic phase, which is considered an "ice" but exists somewhere between a solid and a liquid: while the oxygen atoms occupy fixed lattice positions as in a solid, the hydrogen atoms migrate through the lattice as in a fluid. Until now, scientists have thought that there was only one phase of superionic ice, but scientists in a new study have discovered a second phase that is more stable than the original.

...the simulations show that a phase transition between the bcc and fcc phases may exist at pressures of 1.0 ± 0.5 Mbar.

...Uranus and Neptune we've just done brief flybys with Voyager 2. What we do know is that they have bizarre non-axisymmetric non-dipolar magnetic fields, totally unlike any other planet in our solar system.

Superheated Bose-Einstein condensate exists above critical temperature

Superheated Bose-Einstein condensate exists above critical temperature: In BECs and distilled water, the inhibition of a phase transition at the critical temperature occurs for different reasons. In general, there are two types of phase transitions. The boiling of water is a first-order phase transition, and it can be inhibited in clean water because, in the absence of impurities, there is in an energy barrier that "protects" the liquid from boiling away. On the other hand, boiling a BEC is a second-order phase transition. In this case, superheating occurs because the BEC component and the remaining thermal (non-condensed) component decouple and evolve as two separate equilibrium systems...


Here, the researchers demonstrated that in an optically trapped potassium-39 gas the strength of interactions can be reduced just enough so that the two components remain at the same temperature, but the particle flow between them is slowed down and their chemical potentials decouple. This condition makes it possible for the BEC to maintain a higher chemical potential than the surrounding thermal component, and thus survive far above its equilibrium transition temperature...



In the new study, the physicists experimentally demonstrated that a BEC could persist in the superheated regime... for more than a minute.

Solid or Liquid? Physicists Redefine States of Matter

Solid or Liquid? Physicists Redefine States of Matter: ...the main difference between liquids and solids is the way they respond to shear, or twisting forces. Liquids barely resist shear and can easily be sloshed, whereas solids — regardless of whether they are crystals, quasicrystals or glass — resist attempts to change their shape.

The liquid-solid phase transition, Radin and Aristoff reason, should therefore be marked by the “shear response” of a material jumping from zero to a positive value...

Nanoscale Device Makes Light Travel Infinitely Fast - ScienceNOW

Nanoscale Device Makes Light Travel Infinitely Fast - ScienceNOW: They've developed a tiny device in which the index of refraction for visible light is zero—so that light waves of a particular wavelength move infinitely fast.

The device consists of a rectangular bar of insulating silicon dioxide 85 nanometers thick and 2000 nanometers long surrounded by conducing silver, which light generally doesn't penetrate. The result is a light-conveying chamber called a waveguide. Researchers fashioned different devices in which the width of the silicon dioxide ranged from 120 to 400 nanometers...

Right at the cutoff wavelength, things get interesting. Instead of producing a banded pattern, the whole waveguide lights up. That means that instead of acting as waves with equally spaced peaks, or "phase fronts," the wave behaves as if its peaks are moving infinitely fast and are everywhere at once. So the light oscillates in synchrony along the length of the waveguide.

MAKE | What Supercritical Carbon Dioxide Looks Like

MAKE | What Supercritical Carbon Dioxide Looks Like: Carbon dioxide, however, has a fairly accessible critical point at about 90° F, 1100 psi, and thus supercritical carbon dioxide can and does have fairly routine industrial applications, notably the decaffeination of coffee. But the really cool part is that, at those temperatures and pressures, it’s not too hard to build a pressure vessel from transparent materials that will actually let you get a good look at a supercritical fluid.

Single molecule can shift the phase of a laser beam

Single molecule can shift the phase of a laser beam: To demonstrate how a molecule can change the phase of a light beam, the researchers detected organic molecules (dibenzanthanthrene) embedded in a solid matrix by performing coherent extinction spectroscopy at liquid helium temperature (near absolute zero). In this procedure, they tightly focused an excitation laser beam on the molecular sample in front of a mirror.
Next, the researchers arranged an interferometer consisting of two laser beams traveling the same path but with a small (115 MHz) frequency offset. As the laser frequencies traveled through the resonance of a single molecule, the researchers observed that the phase of one of the two interferometer beams was shifted by three degrees.

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."

Spin liquids: an exotic quantum state of matter | KurzweilAI

Spin liquids: an exotic quantum state of matter | KurzweilAI: The researchers found a “kaleidoscope” of phases that represent the lowest-energy states that are allowed given the magnetic interactions... a change in the strengths of the interactions among the spins (the J1 and J2 parameters) results in different phases. For example, one simple solution is an antiferromagnet, where the spins are anti-aligned.

But one phase turns out to be a true quantum spin liquid having no order at all. When J2 is between about 21% and 36% of the value of J1, frustration coaxes the spins into disorder; the entire sample co-exists in millions of quantum states simultaneously.

In a major breakthrough, scientists control light propagation in photonic chips

In a major breakthrough, scientists control light propagation in photonic chips: "We're very excited about this. We've engineered and observed a metamaterial with zero refractive index,' said Kocaman. 'What we've seen is that the light disperses through the material as if the entire space is missing. The oscillatory phase of the electromagnetic wave doesn't even advance such as in a vacuum — this is what we term a zero-phase delay...'"
...They... cascaded the negative index medium with a positive refractive index medium so that the complete nanostructure behaved as one with an index of refraction of zero.

How To Spot a Rotating Black Hole - Technology Review

How To Spot a Rotating Black Hole - Technology Review: Black holes do strange things to the fabric of space time, particularly if they are rotating. One well known effect is that a rotating black hole drags this fabric with it, intermixing space and time in nearby regions.

Today, Fabrizio Tamburini at the University of Padova in Italy and a few pals say this ought to have a significant effect on light that gets caught up in this process and is then emitted from the disc of accreting matter around a rotating black hole. They say the rotation ought to distort the wave front and phase of this light, while imparting orbital angular momentum to the beam.