A superconductor carries current with no resistance below some temperature, and that temperature is the number the field has chased for over a century. The record quoted here is the ambient-pressure one: the temperature reached at ordinary atmospheric pressure, which is the pressure anything a person can build operates at. Results obtained inside a diamond anvil cell at a hundred thousand atmospheres are real measurements and a separate list.
Every material that has held it
Eight materials, in order of first report. Each value is the published transition temperature at ambient pressure.
| Year | Material | Tc |
|---|---|---|
| 1911 | Hg | 4.2 K |
| 1941 | NbN | 16 K |
| 1954 | Nb₃Sn | 18.3 K |
| 1973 | Nb₃Ge | 23.2 K |
| 1986 | La-Ba-Cu-O | 35 K |
| 1987 | YBCO | 92 K |
| 1988 | Tl-2223 | 122 K |
| 1993 | Hg-1223 | 135 K |
| Reported separately · pressure-prepared | ||
| 2026 | Hg-1223pressure-quenched, survives about three days at 77 K | 151 K |
Published measurements compiled on Reference, not platform predictions. Download the CSV.
Two eras, not one curve
Progress was not steady. From 1911 to 1973 the conventional superconductors raised the record from 4.2 K to 23.2 K, about nineteen kelvin in sixty-two years. Then the copper-oxide ceramics arrived, and in the seven years from 1986 to 1993 the record went from 35 K to 135 K.
The commercially important line is crossed inside that second era. Liquid nitrogen boils at 77 K and liquid helium at 4.2 K, and nitrogen costs a small fraction of helium per liter and needs a fraction of the plant around it. A conductor that works above 77 K changes what a project can afford, and that is what makes YBCO in 1987 the entry that turned the subject into an industry.
Then it stopped
Hg-1223 reached 135 K in 1993, and that figure stood as the durable ambient-pressure record for 33 years. Conductor manufacturing and magnet engineering advanced a long way over the same period. The transition temperature did not.
What happened in 2026
A group in Houston reported 151 K at ambient pressure in Hg-1223, the same compound that had held the record since 1993. The material was compressed in a diamond anvil cell, then decompressed at low temperature so that the pressure-prepared phase was retained. The process, not a new composition, is what produced the number. Published in PNAS, doi 10.1073/pnas.2536178123.
The phase survives about three days at 77 K and is lost above 200 K, and the reported samples are flakes tens of microns across. It extends the measured record. It does not establish a durable or manufacturable conductor, and it is listed apart from the chain above for that reason.
The useful reading is that the record fell to a process applied to a thirty-three-year-old compound rather than to a new material. Whether a superconductor can be made, at length, in a form that survives its own operating conditions, is a question about processing as much as about composition. A search over materials that ignores the second half returns work rather than answers.
The gap that is left
A warm room is about 293 K. The durable record is 135 K. The distance between them is 158 kelvin, and closing it is the open problem the field is named after.
Using this data
- The table above is published as a CSV, with the pressure-quenched result kept separate and its conditions preserved.
- The chart drawn from the same numbers is on the reference page.
- Cite the original publication for any single value rather than this page. Each is a published result by a group with no stake in what we are doing.