For 30 years, the number sat untouched: 133 kelvin, or about minus 140 degrees Celsius. That was the highest temperature at which any material had ever been shown to conduct electricity with zero resistance at normal atmospheric pressure. The record belonged to a mercury-based ceramic called Hg-1223, first characterized in the mid-1990s, and despite enormous global effort, nobody could push it higher without applying crushing force that made the result useless outside a laboratory.
Now a team at the University of Houston has broken through. In a peer-reviewed paper published in PNAS, the researchers report that a modified version of the same Hg-1223 compound superconducts at up to 151 kelvin at ambient pressure, an 18-degree leap that represents one of the largest single advances in the field’s modern history. A detailed preprint on arXiv describes the experimental protocol and confirms the result is reproducible across multiple samples.
The University of Houston has been a powerhouse in high-temperature superconductivity research for decades, with a program built around physicist Ching-Wu “Paul” Chu, who helped launch the field in the late 1980s. The new work extends that legacy with a technique the team calls a pressure-quench protocol, or PQP.
How the pressure-quench protocol works
The concept is deceptively simple. The Houston researchers first synthesized Hg-1223 under high pressure, which rearranges atoms in the crystal lattice and shifts oxygen into positions that favor superconductivity at higher temperatures. Then, instead of slowly releasing the pressure and watching those favorable arrangements collapse, they rapidly quenched it, locking the high-pressure structure in place before it could relax.
The result is a ceramic pellet that retains the structural fingerprints of its high-pressure birth but sits comfortably on a benchtop at ordinary atmospheric conditions. Earlier experiments dating back to 1993 had shown that Hg-1223 could superconduct above 150 K while pressure was actively applied. The Houston team’s breakthrough is that they found a way to keep that performance after the pressure was gone.
A companion Perspective piece in PNAS frames the 151 K result as a milestone on a longer roadmap toward room-temperature superconductivity, roughly 300 K. That commentary emphasizes a distinction that matters enormously for practical applications: ambient-pressure stability versus laboratory-only curiosities. Hydrogen-rich compounds have been shown to superconduct at even higher temperatures, but only under pressures found deep inside planetary interiors, conditions no engineer can build a power grid around.
Why 18 degrees is a big deal
In most areas of science, an 18-degree temperature shift would barely register. In superconductivity, where progress has often been measured in fractions of a degree per year, it is seismic.
The practical significance comes down to thermal margin. Superconducting devices are typically cooled with liquid nitrogen, which boils at 77 K. The old 133 K record already sat well above that threshold, but every additional degree of margin makes cryogenic engineering simpler, cheaper, and more forgiving. At 151 K, engineers have a wider buffer against temperature fluctuations, which translates to less insulation, lower cooling costs, and greater reliability in real-world settings like MRI machines, particle accelerators, and power transmission lines.
The jump also carries symbolic weight. The 133 K ceiling had become something of a psychological barrier in the cuprate superconductor community. Dozens of research groups worldwide had tried chemical substitutions, novel annealing procedures, and thin-film techniques to nudge it upward. None succeeded at ambient pressure. The fact that the Houston team broke through not by discovering a new material but by processing a known one differently suggests that latent performance may be hiding in other well-studied compounds, waiting for the right synthesis trick to unlock it.
What has not been proven yet
The result, published in May 2026, has not yet been independently replicated by an outside laboratory. In superconductivity research, independent reproduction is the dividing line between a lasting advance and a contested claim. The field still carries scars from high-profile retractions, most recently the controversy surrounding room-temperature superconductivity claims by Ranga Dias at the University of Rochester, which were retracted by Nature in 2023, and the brief frenzy over LK-99, a copper-substituted lead apatite that turned out not to be a superconductor at all. The Houston group’s work is far more methodologically detailed than either of those episodes, but the scientific community will rightly withhold full confidence until other teams reproduce the pressure-quench protocol and measure the same transition temperature.
Long-term stability is another open question. The pressure-quenched samples were characterized shortly after preparation, but the published data do not show how the superconducting phase behaves over weeks or months. Metastable crystal structures can slowly relax toward their equilibrium state, and the oxygen sublattice configuration created by the quench could be vulnerable to that kind of drift. Whether the 151 K performance holds, degrades, or shifts over time will determine how seriously device engineers take the result.
Critical current density, the amount of electrical current a superconductor can carry before its zero-resistance state breaks down, is not reported in the primary sources. This metric is what separates a physics discovery from an engineering material. Grain boundaries, defects, and microstructural irregularities can all choke current flow even in a sample with a high transition temperature. Without those numbers, it is impossible to say whether pressure-quenched Hg-1223 could ever wind up inside an MRI coil or a power cable.
The full raw resistivity and magnetization datasets are referenced in the PNAS Supporting Information but are not reproduced in available summaries. Specialists will want to examine the sharpness of the superconducting transition, the magnitude of the Meissner effect, and the behavior under applied magnetic fields before rendering a final judgment on sample quality and phase purity.
The path from 151 K to something useful
One of the most intriguing questions raised by the Houston work is whether the pressure-quench protocol can eventually be replaced by a purely chemical route. If the favorable oxygen sublattice arrangement can be reproduced through targeted cation substitution or alternative annealing atmospheres, the need for high-pressure equipment disappears entirely. That would open the door to producing high-temperature superconductors with standard ceramic processing tools, the kind already used in factories that make electronic components.
If, on the other hand, the quenched structure turns out to be accessible only through the pressure route, scalability will depend on the cost and throughput of high-pressure synthesis followed by rapid decompression. That is not an insurmountable barrier, but it is a significant one, and it would limit adoption to applications where the performance gains justify the manufacturing complexity.
The broader question is whether similar pressure-quench strategies could work in other cuprate families or in entirely different classes of superconductors. The Houston team has demonstrated a principle: structures stabilized under extreme conditions can sometimes be frozen in and recovered at ambient pressure. If that principle generalizes, it could rewrite the playbook for how researchers search for new superconducting materials, shifting the focus from discovering new compounds to finding clever ways to process existing ones.
Where the field stands now
The 151 K result is a serious, technically detailed claim that has cleared peer review at one of the world’s most prominent scientific journals. It comes from a research group with a decades-long track record in exactly this area of physics. Those are strong credentials. But superconductivity has burned the public before, and the field’s own standards demand independent confirmation, stability data, and current-carrying measurements before any result earns the label of settled science.
What makes this particular advance worth watching closely is not just the number on the thermometer. It is the method. If pressure-quenching proves robust and reproducible, it hands the community a new tool for extracting performance from materials that were thought to have given up all their secrets long ago. The 30-year plateau at 133 K was not broken by a miracle material. It was broken by a better question: what if the structure we want already exists, and we just need to figure out how to keep it?
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*This article was researched with the help of AI, with human editors creating the final content.
