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In the pantheon of unconventional superconductors, iron selenide is a rock star. But new experiments by U.S., Chinese and European physicists have found the material's magnetic persona to be unexpectedly mundane.
Rice University physicist Pengcheng Dai, corresponding author of a study of the results published online this week in Nature Materials, offered this bottom-line assessment of iron selenide: "It's a garden-variety iron-based superconductor. The fundamental physics of superconductivity are similar to what we find in all the other iron-based superconductors."
Conclusion - Data - Neutron - Experiments - Year
That conclusion is based on data from neutron scattering experiments performed over the past year in the U.S., Germany and the United Kingdom. The experiments produced the first measurements of the dynamic magnetic properties of iron selenide crystals that had undergone a characteristic structural shift that occurs as the material is cooled but before it is cooled to the point of superconductivity.
"Iron selenide is completely different from all the other iron-based superconductors in several ways," said Dai, a professor of physics and astronomy at Rice and a member of Rice's Center for Quantum Materials (RCQM). "It has the simplest structure, being composed of only two elements. All the others have at least three elements and much more complicated structure. Iron selenide is also the only one that has no magnetic order and no parent compound."
Dozens - Superconductors - Iron - Atoms - Sheet
Dozens of iron-based superconductors have been discovered since 2008. In each, the iron atoms form a 2-D sheet that's sandwiched between top and bottom sheets made up of other elements. In the case of iron selenide, the top and bottom sheets are pure selenium, but in other materials these sheets are made of two or more elements. In iron selenide and other iron-based superconductors, iron atoms in the central 2-D sheet are spaced in checkerboard fashion, exactly the same distance from one another in both the left-right direction...
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