Researchers discovered a strange signal that revealed how electrons are arranged in iron-based superconducting materials (IBSC), and it could help explain electron response during superconductivity.

Called a nematicity wave, the unusual signal observed by the University of Tokyo researchers could help future researchers better understand electron interaction, especially in iron-based superconducting materials.

One of the challenges in solid-state physics is understanding superconductivity, which the U.S. Department of Energy defines as the flow of electrons through a medium with virtually zero resistance, resulting in almost no heat byproduct and no power losses.

In electronics, this translates to an entirely new class of systems and materials with unparalleled efficiency. The same technology is used on experimental magnetic levitation (MagLev) trains, setting new speed records in Japan as far back as 2015, as reported by Industry Week.

The strange nematicity wave observed in electrons in IBSC materials is reported in the Science journal article "Discovery of Mesoscopic Nematicity Wave in Iron-Based Superconductors," published September 3.

(Photo: Henry Mühlpfordt via Wikimedia Commons)
A high-temperature (liquid nitrogen cooled) superconductor levitating above a permanent magnet (TU Dresden)

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Examining Potential of IBSC Materials

The new study was conducted by Professor Shik Shin and his team from the University of Tokyo's Institute for Solid State Physics. They are examining electron behavior within iron-based superconducting materials, which are promising substances that work better at higher temperatures compared to other superconducting materials.

Also, these researchers are looking for less exotic materials that are easier and cheaper to source and use. For an IBSC sample, its superconductivity can be attained by cooling it down to a couple of hundred degrees below zero, with unusual behavior starting to appear in the process.

"As IBSCs cool down to a certain level, they express a state we call electronic nematicity," explains Professor Shin in a University of Tokyo news release via PhysOrg. "This is where the crystal lattice of the material and the electrons within it appear to be arranged differently depending on the angle you look at them, otherwise known as anisotropy."

He additionally explained that the team expects electrons to be closely related to the arrangement of the surrounding crystal lattice. However, based on the latest observations, this does not seem to be the case.

Visualizing IBSC on Microscale, Finding Nematicity Wave

To make the groundbreaking observation, researchers used a specially developed technique called laser photoemission electron microscopy (laser-PEEM) to visualize an IBSC sample on the microscale.

While researchers found the expected pattern that repeats every few nanometers on the sample, they found something more - an electron pattern that repeats once every few hundred nanometers on top of the smaller, expected pattern.

While the electron nematicity wave has been observed to be disparate from the crystalline structure of the IBSC material, researchers are still investigating what this could imply for the material.

However, researchers believe that this could lead to theoretical and experimental inquiries that could further clarify the phenomenon of superconductivity, specifically how an electron finds and forms pairs at extremely low temperatures.

If nematicity waves could offer a clue about electron behavior in IBSC materials, then it is important to understand this pattern.


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