A fundamental feature of superconductivity has recently been observed at temperatures much higher than scientists thought possible.
Physicists have discovered that electrons pair up in the way they do in superconductors in an unexpected material. Above incredibly cold temperatures, similar materials allow superconductivity to occur.
Superconductivity describes the way electrons move through a material without any resistance and thus losing energy. We have observed this phenomenon in many different materials, but there is one problem. It seems that we can only make it happen at very low temperatures, close to absolute zero (-273.15°C, or -460°F), or slightly cooler temperatures with a lot of pressure.
Although the electrons in the newly tested materials have not achieved resistance-free flow, their coupling is a crucial step required for this to happen, potentially leading to superconductivity that would not require large equipment.
“The electron pairs tell us that they are ready to become superconductors, but something is preventing them from doing so.” Physicist Ke Jun Shaw says From Stanford University. “If we can find a new way to synchronize the pairs, we might be able to apply that to building superconductors.”
The material is a multilayer crystal, or copper sulfate, called neodymium cerium copper oxide (Nd).2−xbadSCopper oxide4). At low temperatures, the crystal exhibits superconductivity, but becomes significantly more resistant at higher temperatures.
Now, for superconductivity to work, electrons need to have their quantum identity entangled, turning them into what is called Cooper’s husbandOnly then could they smoothly move through the atomic forest without any effort.
Conventional superconductors, which exhibit superconductivity at temperatures below about 25 Kelvin (-248 °C, or -415 °F), entangle their electrons through vibrations in the underlying material.
Cuprates are unconventional superconducting materials, exhibiting superconductivity at temperatures up to 130 K. Scientists believe that another mechanism is responsible for the pairing of electrons in these materials, but the exact process remains somewhat mysterious.
The neodymium-cerium-copper oxide that Xu and his team studied is similar to a conventional superconductor in that it does not exhibit the phenomenon above 25 K, allowing them to study phases of superconductivity. As electrons become entangled, they become less resistant to being ejected from the material as the temperature increases; that is, the material loses energy at a lower rate. This is known as the coupling gap.
The team observed that their material retains more energy at temperatures up to 140 Kelvin (-133 degrees Celsius, or -207 degrees Fahrenheit) — much higher than the superconducting transition temperature of 25 K. This suggests that electrons form Cooper pairs at relatively high temperatures.
But it’s still not clear what drives this coupling. It may not be the specific material that leads us to room-temperature superconductivity. But it could be a way to find answers and the material of the future.
Superconductivity at ambient temperatures is of great importance. Imagine 100% energy efficiency – we could reduce the size of the electrical circuits required to transport electrons, and pack more energy into a smaller space for faster, cheaper technology.
But cracking the code has been extremely difficult. We have seen some alleged discoveries, such as the much-hyped LK-99, but they have all come to nothing.
Progress is likely to be more gradual—observing some feature of superconductivity in higher-temperature materials, figuring out why it happens, and proceeding step by step.
“Our findings open a potentially rich new way forward.” Physicist Chi Shun Shen says: From Stanford University.
“We plan to study this coupling gap in the future to help design superconductors using new methods. On the one hand, we plan to use similar experimental approaches at SSRL to gain more insight into this incoherent coupling state. On the other hand, we want to find ways to manipulate these materials to force these incoherent pairs into synchrony.”
The research was published in sciences.
