New Possibilities Found for Room-Temperature Superconductivity

Room-temperature superconductivity

Researchers find that triggering superconductivity with a flash of light requires the same fundamental physics at work in the more stable states needed for devices, opening up a new path toward creating room-temperature superconductivity.

Researchers can learn more about a system by jolting it into a somewhat unstable state– scientists call this “out of equilibrium”– and after that, watching what occurs as it settles back down right into a more stable state, just like people can learn more about themselves by stepping out of their comfort zones.

A look into Superconductivity

Experiments with the superconducting material yttrium barium copper oxide, or YBCO, have shown that under particular conditions, smacking it out of equilibrium with a laser pulse enables it to superconduct– conduct electrical current with no loss– much closer to room temperature than scientists expected. Scientists have worked on room-temperature superconductors for over three decades, which may be a significant breakthrough.

However, do observations of this unstable state have any relevance to how high-temperature superconductors might function in real life, where applications such as power lines, maglev trains, particle accelerators, and medical equipment require their stability?

A recent research study published in Science Advances suggests that the solution is yes.

According to Jun-Sik Lee, a staff researcher at the Department of Energy’s SLAC National Accelerator Laboratory, individuals thought that although this sort of study was useful, it could have been more promising for future applications. Jung-Sik Lee is also the leader of the international research crew that conducted the study.

“Now we have revealed that the fundamental physics of these unstable states are extremely comparable to those of stable ones. This opens up substantial opportunities, including the possibility that other materials could also be pushed into a transient superconducting state with light. It is a fascinating state that we can not see any other way.”

What does normal look like?

YBCO is a copper oxide compound, likewise known as cuprate. It is a member of a family of materials found in 1986 that conduct electricity with no resistance at temperatures much greater than researchers had previously considered possible.

Like conventional superconductors, which had been found more than 70 years earlier, YBCO changes from a normal to a superconducting state when cooled below a certain transition temperature. Then, electrons pair and develop a condensate– a kind of electron soup– that easily conducts electricity. Researchers have a solid theory of how this happens in old-style superconductors, yet there is still no agreement about exactly how it works in unconventional ones like YBCO.

One way to dive into the issue is to research the normal state of YBCO, which is plenty weird in its own right. The normal state has a variety of complex, interwoven phases of matter, each with the potential to aid or hinder the transition to superconductivity, that jolt for dominance and often overlap. In a few of those phases, electrons appear to acknowledge each other and act collectively as if they were dragging each other.

It’s a genuine tangle, and scientists wish that understanding it better will clarify how and why these materials become superconducting at temperatures much higher than the theoretical limit predicted for conventional superconductors.

Particle normal states

It is not easy to look into these fascinating normal states at the warm temperatures where they occur, so scientists generally cool their YBCO samples to the point where they end up being superconducting, then turn off the superconductivity to restore the normal state.

The switching is usually done by exposing the material to a magnetic field. This is the preferred approach because it leaves the material in a stable configuration– the type you would need to create a practical device.

Lee stated that superconductivity can likewise be turned off with a pulse of light. This produces a normal state that’s unbalanced– out of equilibrium– where intriguing things can happen from a scientific viewpoint. However, the truth that it’s unstable has made researchers wary of thinking that anything they learn there can likewise be applied to stable materials like the ones required for practical applications.

Waves that stay still

In this study, Lee and his collaborators compared switching approaches– magnetic fields and light pulses– by concentrating on how they influence a peculiar phase of matter referred to as charge density waves, or CDWs, that appear in superconducting materials. CDWs are wavelike patterns of higher and reduced electron density. However, unlike ocean waves, they do not move around.

Two-dimensional CDWs were found in 2012; in 2015, Lee and his collaborators found a new 3D type of CDW. Both kinds are intimately linked with high-temperature superconductivity, and they can work as markers of the transition factor where superconductivity switches on or off.

To compare what CDWs seem like in YBCO when their superconductivity is turned off with light versus magnetism, the research study team did experiments at 3 X-ray light sources.

Properties Of The Undisturbed Material

Initially, they measured the properties of the undisturbed material, including its charge density waves, at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL).

After that, samples of the material were subjected to high magnetic fields at the SACLA synchrotron facility in Japan as well as to laser light at the Pohang Accelerator Laboratory’s X-ray free-electron laser (PAL-XFEL) in Korea so that changes in their CDWs could be measured.

According to SLAC staff researcher and study co-author Sanghoon Song, these experiments demonstrated that exposing the samples to magnetism or light generated similar 3D patterns of CDWs. Although exactly how and why this occurs is still not comprehended, he claimed, the results show that the states induced by either approach have the same fundamental physics. Furthermore, they suggest that laser light could be a good way to produce and discover transient states that could be stabilized for practical applications, including room-temperature superconductivity.

Scientists from the Pohang Accelerator Laboratory and Pohang University of Science and Technology in Korea; Tohoku University, RIKEN SPring-8 Center and Japan Synchrotron Radiation Research Institute in Japan; as well as Max Planck Institute for Solid State Research in Germany likewise added to this job, which the DOE Office of Science funded. SSRL is a DOE Office of Science user facility.

Read The Original Article on Scitech Daily.

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