Research raises new possibilities for causing room temperature superconductivity in light

To study superconducting materials in the “normal” non-superconducting state, scientists usually turn off superconductivity by exposing the material to a magnetic field. SLAC scientists have found that turning off superconductivity with a flash of light produces a normal state with very similar basic physics, which is also unstable and for a short period of room temperature superconductivity. I discovered that I could host the flash of light. These results open new avenues for practical devices to produce sufficiently stable room temperature superconductivity. Credits: Greg Stewart / SLAC National Accelerator Laboratory

Just as people can get out of the comfort zone and learn more about themselves, researchers can learn more about the system by giving it a shock that makes it a little unstable-scientists. This is called “out of equilibrium”-and see what happens. It settles into a more stable state.

in the case of Superconducting material Experiments known as yttrium barium copper oxide (YBCO) have shown that under certain conditions, laser pulses out of equilibrium can cause superconductivity (conducting current without loss) near the room. temperature More than the researchers expected. Given that scientists have been pursuing room temperature superconductors for over 30 years, this can be a major problem.

However, this observation of instability has to do with how high temperature superconductors need to be stable in real-world applications such as power lines, maglevs, particle accelerators, and medical devices. is there?

Research published in Science Advances Today I suggest that the answer is yes.

Jun-Sik Lee, Staff Scientist and Leader of the International Research Team at the SLAC National Accelerator Laboratory at the Department of Energy, said: Do research.

“But now we have shown that the basic physics of these unstable states are very similar to those of the stable state, so this also pushes other materials into a temporary superconducting state. It opens up great opportunities, including possibilities. Light.. It’s an interesting state that can’t be seen otherwise. “

What does it usually look like?

YBCO is a copper oxide compound, or copper oxide, a member of a family of materials discovered in 1986 to conduct electricity with zero resistance at temperatures much higher than scientists thought.

Similar to traditional superconductors discovered over 70 years ago, YBCO switches from the normal state to the superconducting state when cooled below a certain transition temperature. At that point, the electrons pair to form a condensate (a kind of electron soup), which easily conducts electricity. Scientists have a solid theory of how this happens with old-style superconductors, but there is still no consensus on how it works with something unconventional like the YBCO. ..

One way to solve this problem is to look at the normal state of the YBCO. This is very strange in itself. The normal state contains several intricate interwoven phases of matter, each of which can help or impede the transition to superconductivity. Moreover, in some of these phases, the electrons recognize each other and appear to act collectively as if they were dragging each other.

It’s a real entanglement, and with a better understanding of it, researchers can explain how and why these materials become superconducting at temperatures much higher than the theoretical limits expected of conventional superconductors. I hope to clarify.

Because it is difficult to explore these attractive normal states at the warm temperatures in which they occur, scientists typically cool YBCO samples to superconductivity and then turn off superconductivity to normalize them. I will bring it back.

Switching is usually done by exposing the material to a magnetic field. This is the preferred approach because it keeps the material in a stable composition. This is the kind you need to create a working device.

According to Lee, superconductivity can also be turned off with a pulse of light. This creates a normal state that is slightly out of equilibrium, where interesting things can happen from a scientific point of view. However, due to the fact that it is unstable, scientists are wary of thinking that everything they learn there can also be applied to stable materials such as those needed for real-world applications.

Waves as they are

In this study, Lee and his collaborators focus on how they affect the unique phase of matter known as charge density waves (CDWs) appearing in superconducting materials, two switching approaches ( Magnetic field and light pulse) were compared. CDWs are wave-like patterns with higher and lower electron densities, but unlike ocean waves, they do not move around.

The 2D CDW was discovered in 2012, and in 2015 Lee and his collaborators discovered a new 3D type of CDW. Both types are intimately intertwined with high-temperature superconductivity and serve as markers of transition points when superconductivity is turned on or off.

To compare the appearance of the CDW at YBCO when superconductivity is turned off by light and magnetism, the research team conducted experiments with three X-ray sources.

First, SLAC’s Stanford Synchrotron Radiation Source (SSRL) was used to measure the properties of undisturbed materials, including charge density waves.

Next, the material sample was exposed to a high magnetic field at the SACLA synchrotron facility in Japan and exposed to laser light with the X-ray free electron laser (PAL-XFEL) at the Pohang Accelerator Laboratory in South Korea, resulting in a change in CDW. .. measurement.

“These experiments have shown that exposure of a sample to magnetism or light produces a similar 3D pattern of CDW,” said Sanghoon Song, a staff scientist and co-author of the study at SLAC. It is not yet understood how and why this happens, but he said the results show that the states evoked by either approach have the same basic physics.And they laser Light may be a good way to create and explore transient states that can be stabilized for real-world applications (potentially including room temperature). Superconductivity..

Researchers reveal the fourth feature of cuprate superconducting transitions

For more information:
Hoyoung Jang et al, characterization of light-induced normal state by charge density wave of superconducting YBa2Cu3O6.67, Science Advances (2022). DOI: 10.1126 / sciadv.abk0832..

Quote: The study was conducted with light obtained on February 9, 2022 from https: // (February 9, 2022). Raises new possibilities for triggering room temperature superconductivity

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Research raises new possibilities for causing room temperature superconductivity in light

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