Revealing the mysteries of superconductors: Team's new scope takes a closer look

The U.S. Department of Energy's Ames Laboratory has successfully demonstrated that a new type of optical magnetometer, the NV magnetoscope, can map a unique feature of superconductive materials that along with zero resistance defines the superconductivity itself.

That unique feature is the Meissner effect, which is the expulsion of the magnetic field during a material's transition to a superconducting state.

"The Meissner effect is the hallmark signature of a true superconductor, which separates it from a hypothetical perfect metal with zero resistance," said Ruslan Prozorov, an Ames Laboratory physicist who is an expert in superconductivity and magnetism at low temperatures. "That is fine in textbooks and in principle, but in real superconductingmaterials the Meissner effect is quite complicated. Robust screening of a magnetic field by a superconducting sample and Meissner expulsion upon cooling in a magnetic field can be confused. This effect is actually very weak and fragile and difficult to observe."

Until now, physicists have been able to observe the Meissnereffect, but were unable to visualize its spatial distribution in the material and how that might vary between different superconducting compounds. Now it is possible to map unique and distinguishing features of the Meissner effect, using a very sensitive magnetoscope that takes advantage of the quantum state of a particular kind of an atomic defect, called nitrogen-vacancy (NV) centers, in diamond.