11 April 2014

MagLab scientist publishes new superconducting study

MagLab physicist Oskar Vafek’s latest groundbreaking work on superconductivity.


TALLAHASSEE, Fla. — MagLab physicist Oskar Vafek’s latest groundbreaking work on superconductivity — “Superconductivity on the brink of spin-charge order in doped honeycomb bilayer” — was published in the April 11 online issue of “Physical Review Letters.” In it, Vafek and his collaborators explore how a bilayer of graphene could be coaxed into becoming an unconventional superconductor, or a material that will conduct electricity without resistance at certain cold temperatures.

Oskar VafekOskar Vafek.

“I study what happens when you add electrons, or take electrons away, from a material, to see if that will affect the material’s ability to superconduct,” Vafek said. “I am a theorist trying to understand, among other things, the mechanism of unconventional superconductivity.”

Conventional superconductors are materials that typically require the temperature to drop to about 30 Kelvin (or negative 243 degrees Celsius) or below in order to superconduct. The high-temperature superconductors Vafek is interested in, however, require only about 100 K (or negative 173 degrees Celsius) in order to superconduct. Such materials are based on copper and oxygen and are called unconventional superconductors.

Vafek, an associate professor of condensed matter physics at Florida State University, uses mathematical models to study superconductivity in exotic compounds. This paper examines bilayer graphene, a strong yet flexible material made up of two layers of carbon atoms that are bonded together in a repeating honeycomb pattern. The work pinpoints the mechanism of unconventional superconductivity in this model system, and may provide insights into the more general question of how such superconductivity emerges in other materials.

Two collaborators also worked on the paper with Vafek: James M. Murray and Vladimir Cvetkovic. Both are postdoctoral associates in condensed matter physics at the MagLab.

Murray anticipates a more in-depth look at the same phenomena to be published later this year. That paper, “Excitonic and superconducting orders from repulsive interaction on the doped honeycomb bilayer,” is collaboration between Murray and Vafek.

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.