Physicists Uncover State of Matter in Superconducting Material

A team from Ames Laboratory and the University of Alabama Birmingham has discovered a remarkable new state of matter within an iron pnictide superconductor, revealing a laser-induced formation of collective behaviors that compete with superconductivity around 16 K.

“Superconductivity is a strange state of matter, in which the pairing of electrons makes them move faster,” says Jigang Wang, Ames Laboratory physicist and Iowa State University professor. “One of the big problems we are trying to solve is how different states in a material compete for those electrons and how to balance competition and cooperation to increase temperature at which a superconducting state emerges.”

Wang and his team used laser pulses of less than a trillionth of a second in order to take a series of snapshots using terahertz spectroscopy. The technique, according to the researchers, can be thought of as laser strobe photography, where many quick images reveal the subtle movement of electron pairings inside materials using long wavelength far-infrared light.

“The ability to see these real time dynamics and fluctuations is a way to understand them better,” says Wang, “so that we can create better superconducting electronics and energy-efficient devices.”

Ames Laboratory scientist and ISU professor Paul Canfield, expert in the design and characterization of iron pnictides, created the single crystal sample used in this investigation. Martin Mootz and Ilias E. Perakis, at University of Alabama Birmingham, developed the theory to explain the observation.

The research is further discussed in a paper, “Non-equilibrium Pair Breaking in Ba(Fe1-xCox)2As2 Superconductors: Evidence for Formation of Photo-Induced Excitonic State,” authored by X. Yang, et al., and published in Physical Review Letters.