A Record Unbroken for 30 Years Has Just Fallen: Will This Change the Future of Superconductivity?

After more than three decades, research on superconductivity has reached a new milestone. A group of researchers from the University of Houston and the Argonne National Laboratory (ANL) has raised the maximum temperature at which a material can maintain superconductive properties at ambient pressure from 133 kelvin (approximately -220 °F) to 151 kelvin (approximately -190 °F). The result, published in the journal PNAS, represents a significant step toward the development of more practical superconductors for energy and technology applications.

Superconductivity allows the transport of electrical current without any resistance, eliminating energy losses and enabling applications ranging from electrical grids to high-performance magnets, nuclear fusion systems, and quantum technologies. However, most known materials require extremely low temperatures to function, while those operating near ambient temperature require enormous pressures that are incompatible with practical use.

Diagram of a sample inside a diamond anvil cell showing superconductivity temperature before compression, under high pressure, and after pressure release. The rapid cooling process under pressure causes the sample to reach a higher superconductivity temperature at ambient pressure.

To achieve the new record, researchers worked on the compound Hg-1223, a cuprate superconductor made of mercury, barium, calcium, and copper. This is the same material that held the previous record since the 1990s due to its critical temperature of 133 K at ambient pressure and strong sensitivity to pressure increases.

The sample was placed in a diamond anvil cell and subjected to pressures nearing 30 gigapascals, equivalent to about 300 times those found on the ocean floor. Under these conditions, the critical temperature of the material increases significantly. However, the innovative aspect of the research does not concern the compression phase but rather the subsequent one.

Instead of gradually reducing the pressure, the team adopted a procedure called pressure-quench, rapidly releasing it while the sample was maintained at low temperature. This operation prevented the crystal structure from fully returning to its original configuration, trapping the material in a metastable state that retains some of the changes induced by the high pressure.

Thanks to this treatment, the superconductor continues to operate at 151 K even once returned to ambient pressure, improving the previous record by 18 kelvin and demonstrating that the benefits obtained during compression can be maintained without having to rely continuously on extreme conditions.

To understand the origin of the phenomenon, researchers utilized the Advanced Photon Source at Argonne National Laboratory. The facility's high-intensity X-ray beams allowed for the observation of microscopic changes in the arrangement of atoms during the decompression process.

The analyses highlighted how rapid pressure release generates numerous defects in the crystal structure. While such imperfections are normally considered undesirable, in this case, they seem to contribute to the stabilization of the superconducting state. The material thus retains a kind of "memory" of the configuration acquired under pressure, maintaining a higher critical temperature even in ordinary conditions.

According to Hua Zhou, a physicist at Argonne National Laboratory and a co-author of the study, the result represents an important step towards the development of superconductors that can be used under conditions increasingly closer to ambient conditions. An additional advantage is that the material can now be studied with conventional laboratory tools, without the need to maintain high pressures during experiments.

The new record does not eliminate the need for cryogenic cooling; the 151 kelvin achieved remains well below ambient temperature. However, the demonstration that the beneficial effects of high pressure can be "frozen" in the structure of the material opens a new path for research. The next objective will be to verify whether the adopted protocol can also be applied to other superconductors, particularly those that show even greater increases in critical temperature when subjected to high pressures. If this strategy turns out to be generalizable, it could help accelerate the path toward more efficient superconducting materials suitable for practical use in numerous industrial and scientific sectors.