Physicists have found an Entirely New Type of Superconductivity
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Modern physicists have been chasing superconductivity for quite some time now and recent research shows that they have finally found some success.
A NIMS-Ehime University joint research team succeeded in discovering new materials that exhibit superconductivity under high pressure using material informatics. This opens up a whole lot of new possibilities that were not possible in the past.
Superconductivity
Superconductivity is the ability of a material to conduct electricity with zero resistance. For a material to behave as a superconductor, extremely low temperatures are required. Superconductivity was first observed in 1911 by H. K. Onnes, a Dutch physicist. His experiment was conducted with elemental Mercury at 4o K, which is the temperature of liquid Helium. Since then, some substances have been made to act as superconductors at higher temperatures but the ideal — a material that could achieve that feat normally at a higher temperature — has remained elusive until now.
Superconductivity is well understood in conventional superconductors, which are rigid lattices of positive ions bathed in an ocean of electrons. Electrical resistance occurs when electrons moving through the lattice are slowed down by bumping into it, while superconductivity occurs when the lattice is cooled to a point where it becomes rigid enough for mechanical sound waves, or phonons, to ripple through it. Although traditional superconductors can bring a lot of benefits to us, bulky and expensive material is needed to keep them cool enough for actual use which makes them impractical for commercial use.
Latest Breakthrough
While progress has been slow, scientists have finally made a breakthrough. High-temperature superconductivity is found in new materials nearly at random since there is no theory that would explain the mechanism. In his new work, Viktor Lakhno used bi-polarons as a basis for his experiments. A polaron is a quasi-particle that consists of electrons and phonons. Polarons can form pairs due to electron-phonon interaction. This interaction is so strong that they turn out to be as small as an atomic orbital and are known as the small-radius bi-polarons.
The problem with this theory is that small-radius bi-polarons have a very large mass in comparison with an atom. Their mass is determined by a field that accompanies them in the course of motion and this mass influences the temperature of a superconducting transition.
The New Material
The researching team has now tried to study the spin of electrons in order to figure out a new type of superconductivity. For this reason, they used a material called YPtBi, which has a spin of 3/2 compared to the normal 1/2 spin of electrons. YPtBi was first discovered to be a superconductor a couple of years ago and that in itself was a massive surprise for the scientists because the material doesn’t fulfill one of the main criteria – being a relatively good conductor, with a lot of mobile electrons, at normal temperatures.
Usually, as a material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its surface. Having said that, a magnetic field can still enter its vicinity before quickly decaying away. The degree of penetration is dependent on the nature of the electron pairing happening within the material. The oddity about YPtBi was that when it was warmed up from the Absolute Zero, the amount that a magnetic field could penetrate the material increased linearly instead of exponentially (which is what is normally seen with superconductors). Johnpierre Paglione, a Senior Author of the study, referred to that and said,
“No one had really thought that this was possible in solid materials. High-spin states in individual atoms are possible, but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half.”
Conclusion
Truth be told, we are a long way from having electricity that flows with zero resistance at room temperature. To be of any practical use, superconductors would have to be cheap and more forgiving at higher temperatures. In the meantime, the work opens up some obvious other avenues to pursue. The computational models suggest that yttrium superhydrides could act as superconductors at temperatures above 300 K. Hyunsoo Kim, the Lead Author of the study, expressed hope that this technology could lead to some amazing results by saying,
“We used to be confined to pairing with spin one-half particles. But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting.”
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