When cooled down to almost absolute zero, some materials become superconductors and suddenly transmit electricity without resistance. If we could operate superconductors at room temperature, we could have more efficient electronics and cheaper electric bills, but so far the hottest temperature we can have them at is -135°C (-211°F).
We still don’t understand where the high-temperature superconductivity arises from in materials, which is why scientists are hoping to work it out by studying how atoms and electrons are distributed in the material as it becomes superconductive.
Now, an international team of researchers has had a breakthrough: They discovered that a phase superconductors experience when they are cooled down, called pseudogap, is actually a different state of matter. The results are published in Nature Physics.
"A peculiar property of all these high-temperature superconductors is that just before they enter the superconducting state, they invariably first enter the pseudogap state, whose origins are equally if not more mysterious than the superconducting state itself," said David Hsieh, professor of physics at Caltech and principal investigator of the new research, in a statement. "We have discovered that in the pseudogap state, electrons form a highly unusual pattern that breaks nearly all of the symmetries of space. This provides a very compelling clue to the actual origin of the pseudogap state and could lead to a new understanding of how high-temperature superconductors work."
In superconductors, electrons form pairs when the temperature is low enough. Near absolute zero, the natural vibrations of the material push electrons to overcome their repulsive forces. This doesn’t happen at higher temperatures as the energy from vibrations can’t bind the electrons strongly enough. The crucial step appears to be the pseudogap.
"The discovery of broken inversion and rotational symmetries in the pseudogap drastically narrows down the set of possibilities for how the electrons are self-organizing in this phase," added Hsieh. "In some ways, this unusual phase may turn out to be the most interesting aspect of these superconducting materials."
The next step for the researchers is to look at how electrons are organized in the pseudogap. If that goes well, we might be a step closer to having superconductors at room temperature.