Iron-based molecular sandwich is a new superconductor

29 October 2012

Scientists at Oxford have synthesised a new superconductor in which a molecular spacer layer has been inserted in between layers of iron selenide. Pure iron selenide had already been shown to lose all electrical resistance, but only when cooled below about 8 degrees above absolute zero. As described in a Letter published in Nature Materials, the new compound retains superconductivity at temperatures more than four times higher. The use of the neutron and muon facilities at ISIS was key to characterising the structure by enabling the light atoms to be located and for measurement of some of the fundamental superconducting properties such as the penetration depth.

The work is a collaboration between Simon Clarke's group in the Inorganic Chemistry Laboratory and Stephen Blundell's group in the Physics Department and also involves colleagues at Durham and ISIS.

"Since the discovery of these layered iron-based superconductors in 2008, we have been engaged in an intensive search to optimize the superconducting properties by changing the chemical composition of the spacer layer between the iron-containing layers", explained Simon Clarke. "Our new results are the first characterization of an example in which a molecular species has been incorporated into the structure of such a material. Excitingly, we have discovered that in this case this leads to superconductivity up to 43 kelvin, higher than in any iron selenide-derived compound reported so far."

"We have studied the superconducting properties using a variety of techniques," added Stephen Blundell. "In particular, results using radioactive particles called muons have shown that our new material is a very well-behaved superconductor. Most significantly, the new synthetic route which has now been developed opens up the possibility of further exploitation of related molecular species in this and other systems in order to greatly optimize the superconducting properties in this family."