DailyTech has been extensively covering the breakthroughs in superconductors over the last couple years. The class of materials is very promising in that if someday it could replace conductors, it would mean that electricity could travel at virtually no losses to anywhere in the world. This would result in vast energy savings and allow for dramatically faster computers, free of the burden of resistance-produced waste heat.
Standing in the way of the advances are three critical weaknesses of superconductors. The first and most well known is their temperature dependence. Superconductors must be beneath a critical temperature to superconduct. Typically this critical temperature is extremely low, well beneath the means of even standard liquid nitrogen cooling. The critical temperature is somewhat pressure dependent, so extremely high pressure superconductors can superconduct at higher temperatures.
Recent non-high pressure superconductors have upped the standard Tc to around 138 K (-200 °F). Recently Superconductor.org found a cupric-lead-tin-oxide superconductor, (Sn1.0Pb0.5In0.5)Ba4Tm5Cu7O20, with a Tc of 185.6 K.
The other two lesser known limitations of superconductors are high current and magnetism. At high current, superconductors can cease to function properly. Magnetic fields are particularly deadly to superconductors. Typically, even a small magnet field will revert a superconductor back to a normal conductor.
A new breakthrough from scientists has found a unique class of superconductors which seem to be amazingly almost completely immune to magnetism. This is a significant breakthrough as it could remove one of the largest obstacles to commercializing superconducting.
The new material was first discovered by Japanese researchers early this year that had been looking into iron-superconductors, an atypical choice for superconductor metals, and added a bit of arsenic to the mix. The new iron oxyarsenide -- which also featured oxygen, as the name implies -- superconductor. The new material, which also contained the rare earth metal lanthanum, could superconduct at 26 K (-413 °F).
The researchers were somewhat surprised to find a fully working superconductor with iron as iron typically creates a magnetic field when conducting. Somehow the superconductor was surviving a magnetic field, an unexpected first.
Now researchers David Larbalestier, Alex Gurevich and Jan Jaroszynski, and colleagues in David Mandrus' groupat Oak Ridge National Laboratory in Tennessee and Frank Hunte, a postdoctoral associate at the Applied Superconductivity Center (ASC) of the National High Magnetic Field Laboratory at Florida State University have investigated the phenomena in more depth and synthesized new iron superconductors.
The researchers reported their findings (PDF) in the prestigious journal Nature. Larbalestier, director of the ASC states, "What one would like is a greater selection of superconductors, operating at higher temperatures, being cheaper, possibly being more capable of being made into round wires. Iron and arsenic, both inherently cheap materials, are key constituents of this totally new class of superconductors. We're just fascinated. It's superconductivity in places you never thought of."
The researchers put the new superconductors to the test, placing them within Oak Ridge National Laboratory's 45-tesla Hybrid magnet, one of the most powerful research magnets in existence. Researchers expected the magnet to be sufficient to kill the superconductor, but to their surprise it tolerated it and was healthily superconducting even at the magnetic field's full power.
On a technical side the research yields an even greater mystery, perhaps indicating that we know less about superconduction than we think we do. Superconduction on an atomic level has long been though to occur through so-called "Cooper pairs", paired electrons with opposite spin, momentum, etc. Magnetism was thought to break these pairs. Either iron has some sort of unique way of keeping the pairs bonded, or the current model is incomplete or flawed.
A third possibility is that Cooper pairs are only one method of superconduction, and that the new material utilizes a new mechanism. Says Hunte, "So far based on both theoretical calculations and what we're seeing from the experiments, it seems likely that this is a completely different mechanism for superconductivity."
Possible applications of the new tech include ultra-efficient superconducting motors and power transmission lines. They could also be used in new superconducting magnets, which would open up a new world of research opportunities in diverse fields of science. Hunte states, "The field is completely open. No one knows where this is going to go. If it's found that these materials can support high current densities, then they could be tremendously useful."