Cornell physicists have discovered that minimizing disorder, not varying electron count, is the key factor for controlling the superconductivity in the unique material iron selenide (FeSe), a new insight for understanding high-temperature superconductors. 

Using a new technique to control this iron-based superconductor, researchers in Kyle Shen’s lab have found that iron selenide’s superconducting “dome” – the curve tracing how the superconductivity strengthens and then weakens as the properties are tuned – is more closely linked to resistance caused by imperfections in its crystal lattice rather than the number of electrons flowing through the crystal. Iron selenide could be fundamentally different than other high-temperature (or unconventional) superconductors, the finding suggests. 

“We found that in this material, that dome is driven by factors much different than what you see normally,” said postdoctoral researcher Paul Malinowski, a former Klarman Postdoctoral Fellow in the College of Arts and Sciences (A&S). “It’s not driven by how many electrons you’re adding in, but rather, it’s driven by the obstacles the electrons are hitting – how perfect or imperfect is the crystal lattice?” 

The study “What Controls the Superconducting Dome of Electron-doped FeSe?” published in Proceedings of the National Academy of Sciences Aug. 20 with Malinowski as first author. “It’s an important new result that could give a lot of insight into high-temperature superconductivity,” said Shen, the James A. Weeks Professor of Physical Sciences and Stephen H. Weiss Presidential Fellow (A&S) and director of the Laboratory of Atomic and Solid State Physics, corresponding author of the study. 

Read the full story on the College of Arts and Sciences website.