Eder G. Lomeli

A thin film of iron oxide SrFeO3 sits on a substrate that slightly stretches it. Inside the film, the magnetic moments of atoms twist into a spiral, like a spiral staircase. The strain changed that staircase: the step became shorter, and the axis itself tilted. The reason lies in oxygen.

A layered cake of atomic planes of nickel and oxygen: that's how bilayer nickelates are built. Two such planes are separated by a spacer layer. If an oxygen atom sits in that spacer, it acts as a bridge: it links the layers and triggers a state in which electrons move without resistance.