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New Discovery Challenges Theories for Iron-Based Superconductors

Category: Science & Technology
Posted: 06:27AM

Ever since unconventional, or high temperature, superconductors were discovered researchers around the world have been trying to understand how the phenomenon occurs. Now those at Brookhaven National Laboratory and ORNL have discovered that current theories for iron-based superconductors may be wrong. Instead of finding a link between long-range electronic and magnetic order, the researchers found a liquid-like magnetic state exists prior to superconductivity, and may be linked.

Current theories for high temperature superconductors state that long-range electronic and magnetic order, like patterns of electron spins, precede superconductivity. By doping an iron-telluride superconductor with sulfur though, the researchers were able to prevent the long-range order from forming, but the material still became superconducting as temperatures dropped. What they did observe was ordering only on a very local level, which is liquid-like behavior. This behavior comes from two coexisting and competing magnetic phases interacting within the material. Superconductivity came about after the electronic spin correlations changed, which would be like dancers changing partners on the dance floor.

In addition to challenging theories for iron-based unconventional superconductors, the researchers also got results that may require a revision to the model for electron orbitals in metals. The tight binding model has the electrons existing in rigid energy bands, but the spin-liquid state the researchers observed indicate new electron-orbital hybrids. This is likely the result of the sulfur doping and temperature changes.

Source: Brookhaven National Laboratory

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