Sunday, March 3, 2013

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."

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