TALLAHASSEE, Fla. — Superconductors are materials that can carry electric current without resistance. By increasing the superconductivity to higher temperatures, these materials could have much more widespread applications — with possible uses in electrical grids, next generation supercomputers or levitating trains — but, despite years of research, there is still work to do in understanding the mechanism for achieving superconductivity at higher temperatures.
Scientists have long understood that in superconducting materials, electrons travel together in pairs, allowing them to move smoothly without electrical resistance. Performing experiments at two MagLab sites, researchers from the University of Cambridge, the National High Magnetic Field Laboratory, University of Warwick and the University of British Columbia worked to answer the long-asked question — what is a high temperature superconducting material like before these electrons pair up? Their results are in the June 19th issue of the journal Nature.
Researchers call this "the normal ground state" and this experiment offers the first clear picture that scientists have ever seen. Understanding a material's properties in this normal, non-superconducting state tells us exactly where the electrons begin to pair, which is an important milestone towards the ultimate goal of identifying the "glue" that binds them together. An understanding of this glue would lay the grounds for achieving superconductivity at much higher temperatures.
In this experiment, researchers working with a high temperature superconductor — YBa2Cu3O6+x — needed the strong fields only available at the MagLab to suppress the superconducting effect and uncover its normal ground state.
The most recent experiment was performed in the world-record 100 tesla pulsed magnet housed in the MagLab's Pulsed Field Facility at Los Alamos National Laboratory. Earlier research, though, also included another world-record-setting magnet system — the 45 tesla hybrid magnet at the Florida State University headquarters location.
"We accessed the ground state with the 45 tesla magnet, but continuing our work on the 100 tesla helped us see a much more complete image of the material electronic structure," explained MagLab researcher Neil Harrison.
Data from the 100 tesla shows that the ground state of YBa2Cu3O6 contains unique, corrugated electron pockets that develop from charge density waves, or charge order. These pockets were previously thought to be located in regions of strong superconductivity, but are actually found in "nodal" areas where superconductivity is the weakest.
"This is exciting for us and as an example of the kind of science that can be done in the non-destructive 100 tesla pulsed magnet," said Harrison. "Now, we are seeing theorists taking our measurements very seriously and factoring them into their work."
And that could be the first step to even more discoveries to come.
The National High Magnetic Field Laboratory is the world’s largest and highest-powered magnet facility. Located at Florida State University, the University of Florida and Los Alamos National Laboratory, the interdisciplinary National MagLab hosts scientists from around the world to perform basic research in high magnetic fields, advancing our understanding of materials, energy and life. The lab is funded by the National Science Foundation (DMR-1157490) and the state of Florida. For more information, visit us online at nationalmaglab.org or follow us on Facebook, Twitter, Instagram and Pinterest at NationalMagLab.