Apparently one of the things that happens when a material transitions into a superconducting state is it stretches (by an infinitesimal amount) in the conducting direction. This stretching is not like usual stretching where there’s a change in the actual structure of the material. Rather, it is the bonds between each atom that stretch - pulling them into a slightly different state, one that happens to let electrons flow completely freely (ie superconducting). This “infinitesimal stretching” is usually caused by magnetic alignment, which is induced by super cold temperatures.

But there are a few odd materials, like iron selenide, that don’t seem to show any kind of magnetic alignment despite being able to become superconducting. That’s where the absolute geniuses behind this paper come in. They took a thread of iron selenide and stuck it to a strip of titanium, then physically stretched the titanium. This induced that “infinitesimal stretching” in the iron selenide sample. By examining the sample with X-rays while artificially inducing the stretch, they could detect the mechanism that would usually be the cause of the stretch. Essentially it is sort of like manually spinning the wheels on a car and watching the engine cycle, in order to understand how vehicles work.

Very clever stuff, and it seems like a real advance in understanding superconductivity. The article doesn’t really go into it, but this does suggest there might be a third axis (“super precise tension”), alongside the usual two of “super low temperature” and “super high pressure”, that we can search along to find new superconductors.