Boston, Feb 27 (PTI) The world's only sample of metallic hydrogen created in the lab - touted as the "holy grail of high-pressure physics" - has disappeared, Harvard scientists say.
Last month physicists from Harvard University in the US had claimed to have successfully turned hydrogen into a metal - something researchers had been struggling to achieve for more than 80 years.
However, the team has now announced that the sample has disappeared.
The metallic hydrogen was being stored at temperatures around minus 193 degrees Celsius and at incredibly high pressures between two diamonds.
Further testing caused the diamonds to break and the researchers have not been able to find the metallic hydrogen since.
The sample was only around 1.5 micrometres thick and 10 micrometres in diameter - a fifth the diameter of a strand of human hair.
It is possible that the sample is stable somewhere and missing, researchers said.
Another possibility is that, once the diamonds broke, the hydrogen dissipated back into a gas, which suggests that the material is not stable at room pressure.
"Basically, it's disappeared. It's either someplace at room pressure, very small, or it just turned back into a gas.
We don't know," team leader Isaac F Silvera was quoted as saying by 'ScienceAlert'.
"We're preparing a new experiment to see if we can reproduce the pressures we achieved the first time, and reproduce our metallic hydrogen," said Silvera, who has spent more than 45 years working on metallic hydrogen.