Research quickly confirmed that they demonstrated two additional classic characteristics of the transition to a superconducting state. The material expelled magnetic fields as superconductivity occurred, allowing a magnet placed on a chunk of the material to hover above the surface. And during the transition, their heat capacity – the amount of heat required to raise their temperature by a certain amount – displayed a notable abnormality.
But despite decades of effort with a variety of experimental tools, the fourth signature, which can be seen only on a microscopic scale, remained elusive: the way electrons pair up and condense into a sort of electron soup as the material transitions from its normal state to a superconducting state.
