A group of physicists claim to have observed an unusually long-lived new state of matter in an iron pnictide superconductor, suggestive of a laser-induced formation of collective behaviours competing with superconductivity.
The discovery was made by a joint team of researchers from the US Department of Energy's Ames Laboratory and the University of Alabama, Birmingham.
Superconductivity is the phenomenon of complete disappearance of electrical resistance in certain materials, called superconductors, when they are cooled below a characteristic transition temperature.
The phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Superconductivity was first observed in mercury (Hg), but scientists have now found several metallic elements, intermetallic and organometallic compounds with superconducting properties.
In a superconductor, there is no electrical resistance below transition temperature because no scattering of electrons happens to impede the motion of the current carriers. The current is carried by pairs of electrons known as Cooper pairs.
Below transition temperature, the binding energy of an electron pair causes the opening of a gap in the energy spectrum at the Fermi energy (the highest occupied level in a solid). This gap separates the pair states from the "normal" single electron states.
"Superconductivity is a strange state of matter, in which the pairing of electrons makes them move faster," said Jigang Wang, a physicist at Ames Laboratory.
"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."
In the current study, the research team used ultrafast terahertz pump-probe spectroscopy technique to capture a series of snapshots, which enabled them to study the subtle movement of electron pairings inside iron pnictides superconductor.
In terahertz spectroscopy, laser pulses of less than a trillionth of a second are used.
The results revealed an unusual out-of-equilibrium Cooper pair nonlinear dynamics and a nonequilibrium state driven by femtosecond photoexcitation of superconductivity in iron pnictides.
"The ability to see these real time dynamics and fluctuations is a way to understanding them better, so that we can create better superconducting electronics and energy-efficient devices," said Wang.
The findings of the study are published in the journal Physical Review Letters.
Warming was most pronounced in Siberia region
The tank will be subjected to high stresses and loads via dozens of hydraulic cylinders during testing
'Sunlit wet sidewalk' provides evidence of methane rainfall on the north pole of Saturn's moon Titan
Methane rainfall indicates the start of the summer season in Titan's northern hemisphere
Scientists believe there could be other hydrides or superhydrides with super conducting properties