For more than 30 years, one number stood as a stubborn barrier in superconductivity research: 133 kelvin, or about minus 220 degrees Fahrenheit. No material had managed to superconduct at a higher temperature while remaining under ordinary pressure, despite decades of effort.

Researchers from the University of Houston and Argonne National Laboratory (ANL) have now broken this decades-old record. 

By briefly subjecting a copper-oxide superconductor to extreme pressure and then rapidly releasing it, they achieved superconductivity at 151 kelvin (minus 190 degrees Fahrenheit) under ordinary pressure.

This record matters because superconductors can move electricity without resistance, potentially eliminating energy losses in power grids and enabling more powerful magnets, quantum technologies, and fusion systems. 

However, most superconductors work only at extremely cold temperatures, while the few that approach room temperature require enormous pressures that make them impractical outside laboratories.

The new result suggests that pressure may not have to remain part of the equation. By trapping a superconductor in a pressure-altered state, the researchers preserved a temperature boost that normally disappears the moment the squeezing stops. Here’s how they did it: 

Pushing superconductivity beyond a 30-year-old limit

The team worked with a copper-oxide superconductor called Hg-1223, the same material that has held the ambient-pressure record since the early 1990s.

“To establish a record-high Tc at ambient pressure via PQP, we have chosen the chemically stable Hg1223 since it has the current record-high Tc of 133 K at ambient pressure and, exhibiting a large positive pressure effect on its Tc, 164 K under pressure,” the researchers note.

Researchers squeezed tiny samples inside a diamond anvil cell to nearly 30 gigapascals, roughly 300 times the pressure found at the bottom of the ocean. Under these conditions, the material’s superconducting temperature increased significantly.

The key step came after compression. Instead of slowly returning the material to normal conditions, the researchers rapidly released the pressure while keeping the sample cold.

This pressure-quench process trapped the material in a metastable state, preventing its atomic structure from fully returning to normal. As a result, the sample retained superconductivity at 151 kelvin even after the pressure was completely removed, surpassing the previous record by 18 kelvin.

X-rays revealed why the improvement survived

Breaking the record was only half the challenge. Researchers also wanted to understand why the material kept its improved properties after decompression.

To investigate, the team used the Advanced Photon Source at Argonne National Laboratory. Its highly focused X-ray beams allowed them to examine subtle structural changes inside the material during the pressure-quench process.

The measurements showed that rapid pressure release leaves behind numerous microscopic defects in the crystal structure. Normally, such defects are considered imperfections, but in this case, they appear to help stabilize the superconducting state.

The findings suggest that the material retains a structural memory of the high-pressure environment. Instead of completely relaxing back to its original form, it preserves enough of the pressure-induced arrangement to maintain superconductivity at higher temperatures.

Time to test the pressure-and-release trick further

The new record does not eliminate the need for cooling, and the material still operates far below room temperature. However, the study demonstrates that pressure-enhanced superconductivity can survive after pressure is removed, a result many researchers have long sought.

Unlike superconductors that require constant extreme pressure, the new material can now be examined under ordinary laboratory conditions. This could make it easier for researchers to investigate the mechanisms behind its behavior and explore potential applications.

“With this material still superconducting at normal pressure, scientists can study it with widely available instruments and begin developing technologies that work under everyday conditions,” Hua Zhou, one of the researchers and a physicist at ANL, said.

The next step is determining whether the same strategy can be applied to other superconductors, including materials that achieve even higher transition temperatures under pressure. 

If successful, the approach could provide a practical route toward superconductors that operate under increasingly ordinary conditions.

The study is published in the journal PNAS.

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