A bridge made of two rows of planks bends under the feet of pedestrians, and each step gets a boost from the elastic motion of the deck. A similar principle underlies superconductivity: electrons glide without resistance because the atomic lattice itself adapts to them. In nickel-based materials, this picture has long been elusive. Adding electrons nearly extinguished superconductivity rather than enhancing it.
The authors built a computer model of a double-layer nickelate — a crystal where two layers of nickel and oxygen lie on top of each other like two sheets of paper. They calculated three variants. The first is an ordinary crystal at room pressure. The second is the same crystal compressed to 15 gigapascals (a pressure 150,000 times higher than atmospheric). The third is a heterostructure where one layer is replaced with an aluminum layer. In all three cases, electrons don't quench but ignite the superconducting fire. It burns especially brightly in the heterostructure when electrons are added sparingly.
Such a mechanism is rare. Usually orbitals work independently, but here one helps the other, and together they produce strong pairing. Interestingly, the record superconducting transition temperature (about 50 kelvins, minus 223 degrees Celsius) occurs not when electrons are abundant, but in a region of scarcity — the so-called underdoped regime. This defies intuition, but quantum-level calculations show exactly this picture. Now it's up to experimentalists: if they can grow such a heterostructure and measure its resistance, we'll have a new class of superconductors that don't require enormous pressure.
The pressure of 15 gigapascals used in the calculations is comparable to that at the bottom of the Mariana Trench, multiplied by 1,500. At such compression, interatomic distances shrink by a few percent, completely changing the properties of electrons.
In Peter Watts's novel Blindsight, an alien ship uses superconducting cables at room temperature — still science fiction, but nickelate calculations bring it closer.