An Invisible ‘Demon’ Lurks in an Odd Superconductor
A few years ago, the researchers decided to put a superconducting metal called strontium ruthenate in their crosshairs. Its structure is similar to that of a mysterious class of copper-based “cuprate” superconductors, but it can be manufactured in a more pristine way. While the team didn’t learn the secrets of the cuprates, the material responded in a way that Ali Husain, who had refined the technique as part of his doctorate, didn’t understand.Husain found that ricocheting electrons were sapped of their energy and momentum, which indicated that they were setting off energy-draining ripples in the strontium ruthenate. But the waves defied his expectations: They moved 100 times too quickly to be sound waves (which ripple through atomic nuclei) and 1,000 times too slowly to be charge waves ...