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Doping a Superconductor isn't like Doping a Semiconductor

Minute chemical substitutions are used to induce superconductivity in many materials, but the precise role of these dopants in iron-pnictide superconductors is an ongoing debate. In semiconductors, doping allows charge carrier concentrations to be controlled enabling electronic devices to be created. However, dopants in iron-arsenide superconductors do not simply impact charge carrier concentrations.

Putting Pressure on Iron-Arsenide Superconductors

Stepping on a sample, particularly in high heels, is not something most researchers would do.  However, by applying pressure comparable to that generated under a stiletto heel, researchers discovered that the low temperature properties of an iron-arsenide-based superconductor where cobalt is substituted for some of the iron, Ca(Fe1-xCox)2As2, can be changed from antiferromagnetic, to superconducting to non-magnetic in a highly controllable manner.

Metamaterials put the Brakes on Light

Designing methods to slow down electromagnetic signals just got easier with a new model that predicts how light will absorb and scatter from devices made from metamaterials. Metamaterials are built from small, engineered structures that, in some ways, mimic the role of atoms, yet can manipulate light in ways not seen in conventional materials. Slowing down light can arise in metamaterials through a process known as electromagnetically induced transparency, when destructive coupling occurs between a bright resonator and a dark resonator.

Engineering a Light Touch

Researchers have found a way to enhance the force of light on matter. Most of the time the momentum of light and the associated forces are too small to notice, but at the nanoscale the effect can be quite large, and researchers have used these forces to dynamically manipulate optical waveguides at the nanoscale. Optical forces decay significantly, however, as the distance between the waveguides increases and become too small for all-optical device actuation at larger separations.

The Golden Key

Gold atoms can be the key to making new materials with fascinating and frequently beautiful arrangements of atoms. For example, materials made from gold, sodium and gallium contain gold atoms arranged into tetrahedra, rods of hexagonal stars, or diamond-like three-dimensional frameworks.  For certain gold concentrations, gold interacts in a novel way with sodium and stabilizes the formation of icosahedra.

Magnetic Memory Moves into the Ultra-Fast Lane

Researchers have found a trick that could make writing data to a hard disk as much as a thousand times faster. Recording information in today’s magnetic memory and magneto-optical drives uses an external magnetic field and/or a laser that heats up tiny spots, one at a time, to the point where the magnetic field can switch the magnetic ordering, to store single binary digits. The speed of the magnetic switching is limited by how long it takes the laser to heat the spot close to its Curie point and the external field to reverse the magnetic region.

Cutting Biofuel Production Costs

Working to use sunlight to convert biomass to biofuels, researchers have found a pathway toward reducing the energy costs associated with making renewable biofuels. To achieve this, they designed semiconducting nanorods that act as light harvesting antennas, and attached metal nanoparticles that are activated by energy from the sun.

Tinkering with Zinc

Scientists have made air-stable compounds that should not be stable in air. Custom-designed carbon chains bonded to zinc control the rate and selectivity of reactions with oxygen and lead to the formation of novel stable zinc peroxides.

Shaken Not Stirred — A Superconducting Material also Shows Promise for Hydrogen Storage

A new recipe for storing hydrogen involves taking magnesium diboride, putting it in a container, adding some hydrogen and ball bearings, and shaking vigorously. Unlike other methods, heating the mixture is not required. Creating a room-temperature-stable, solid-stored hydrogen fuel has been described as one of the grand challenges of science. MgB2 (previously known primarily for its high-temperature superconductivity) has a hexagonal structure of boron sheets separated by layers of Mg.


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