Modern superconductors, such as iron selenide (FeSe), are still not fully understood. They remain one of the most active areas of research in quantum materials.
FeSe, in its three-atoms-thick monolayer form, poses some unusual superconductive properties. In bulk form, it becomes a superconductor at 8 Kelvin or -265 Celsius. As a monolayer, though, it starts superconducting at about 70 Kelvin, or 203 degrees below zero – still very chilly, but moving in the right direction.
In a new study, in collaboration with the University of British Columbia, Yale scientists shed light on the behavior of electrons in this system. They uncovered some interesting clues about superconductivity. The study could prove to be key to understanding superconductivity itself.
Scientists used one of the most advanced synchrotron light sources in the world to study the material’s electronic structure closely. They have shown a series of electronic states, known as replica bands, which are modified by electron-phonon coupling.
These can be traced back to the electronic orbitals of atoms in the monolayer. The quality of the material and the sensitivity of the measurements allowed the scientists to analyze these effects quantitatively for the first time.
They found that the existing theories of superconductivity do not satisfactorily explain the intensity of these replica bands.
Besides shedding light on this vital system, scientists think of the need for further study to fully unravel the origin of enhanced superconductivity.
Charles Ahn, the John C. Malone Professor of Applied Physics, Mechanical Engineering & Materials Science & Physics, said, “It’s a timely result that takes advantage of recent advances in large-scale spectroscopic facilities. The results test several theories, though we still don’t have a definitive answer. This experiment provides another piece of the puzzle.”
Existing superconductors use liquid helium, which is very expensive, to cool them down to low enough temperatures. The research team’s discovery is a step toward changing that.
Fred Walker, a Senior Research Scientist in Applied Physics, said, “One of the really exciting things in the field now is the possibility of getting a superconductor up to room temperature. And understanding the mechanisms for superconductivity at this detailed level looks like an exciting route to achieving that.”
The study is published in Nature Communications.