Cornell physicists have found that imperfections in the crystal structure of iron selenide may control its superconductivity more than the number of electrons flowing through the material. The finding could change how researchers understand one class of high-temperature superconductors.
The team used a new technique to tune iron selenide, also known as FeSe, and examined its superconducting “dome” — the curve showing how superconductivity strengthens and then weakens as a material's properties change. Researchers found that the curve tracked resistance caused by disorder in the crystal lattice more closely than changes in electron count.
Crystal quality emerged as the key factor
High-temperature, or unconventional, superconductors can carry electrical current without resistance under conditions that differ from conventional superconducting materials. Scientists study the shape of a material's superconducting dome to understand what controls that behavior.
In iron selenide, the Cornell team found that superconductivity depended heavily on the obstacles electrons encountered as they moved through an imperfect crystal. Postdoctoral researcher Paul Malinowski said the result differs from the usual pattern in which researchers focus on how many electrons are added to a material.
The work suggests iron selenide may operate differently from other unconventional superconductors. Minimizing disorder, rather than changing electron concentration, could therefore be the more important way to control the material's superconducting properties.
Study appeared in national journal
The study, “What Controls the Superconducting Dome of Electron-doped FeSe?” was published Aug. 20 in the Proceedings of the National Academy of Sciences. Malinowski, a former Klarman postdoctoral fellow in Cornell's College of Arts and Sciences, was the first author.
Kyle Shen, director of Cornell's Laboratory of Atomic and Solid State Physics, was the corresponding author. Shen is the James A. Weeks Professor of Physical Sciences and a Stephen H. Weiss Presidential Fellow in the College of Arts and Sciences.
Shen said the result could provide new insight into high-temperature superconductivity. The research narrows attention toward crystal-lattice disorder as scientists work to explain why unconventional superconductors behave as they do.
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