Pairing of the "glue" for electrons in the high-temperature iron-based superconductors studied

Recently published research by a team of scientists led by the Ames Laboratory of the US Department of Energy sheds more light on the nature of high-temperature iron superconductivity.

Current theories suggest that magnetic fluctuations play a very important role in the determination of superconducting properties and even act as a "matching glue" in iron-based superconductors.

"A metal becomes a superconductor when normal electrons form what physicists call Cooper pairs." The interactions responsible for this bond are often referred to as "pairing glue." Determining the nature of this glue is the key to understanding , optimize and control superconducting materials, "said Ruslan Prozorov, Ames laboratory physicist, expert in superconductivity and magnetism.

Scientists from Ames Laboratory, Nanjing University, the University of Minnesota and the École Polytechnique have focused their attention on high quality monocrystalline samples of a family of high temperature superconductors to iron arsenide extensively studied. They sought an experimental approach to systematically disrupt the ordered magnetic, electronic and superconducting states; while keeping the magnetic field, temperature and pressure unchanged.

They chose a not so obvious direction: to deliberately induce a disorder in the crystal lattice, but in a controlled and quantifiable way. This was done at the SIRIUS electron accelerator of the École Polytechnique. Scientists have bombarded their samples with fast electrons moving at ten per cent of the speed of light, creating collisions that cause atoms to move and result in desired "spot" defects. The method, adopted by the Ames laboratory at the very beginning of iron superconductivity research, is a means of pushing or pushing the system and measuring its response. "Think of it as another" button "on which we can turn, leaving the other important parameters unchanged," said Prozorov.

In previous and related research published in Nature Communications In 2018, and using a similar approach of probing the system by disorder, the team examined the coexistence and interaction of superconductivity and charge density waveform (CDW), another quantum order competes with superconductivity. There, they discovered a complex relationship in which CDW competes for the same electronic states, but also helps superconductivity by softening the phonon modes acting as a superconducting glue in this case (a NbSe2 superconductor).

In the present work, traveling magnetism (spin density wave) also competes with superconductivity for electronic states, but offers magnetic fluctuations as glue.

The team found that the added disorder resulted in a substantial suppression of magnetic order and superconductivity, indicating a significant role of magnetism in high temperature superconductivity.

The research is discussed in more detail in the paper, "Interaction between superconductivity and itinerant magnetism in under-doped cells._{1 time}K_XFe₂As₂ (x = 0.2) probed by the response to a controlled spot disorder ", written by R. Prozorov, M. Koïczykowski, A.A. Tanatar, H.H. Wen, R.M. Fernandes and P.Canfield, and published in Quantum Nature Materials.