A month after two Harvard physicists published results detailing the synthesis of the first-ever sample of solid metallic hydrogen, the researchers have lost the sample after trying to further analyze it.
In late January, Isaac F. Silvera and Ranga P. Dias—a Harvard physics professor and postdoctoral researcher respectively—published their discovery of the potential “superconductor,” which could transform the way electricity is conducted. In a paper in the journal Science, they wrote that under extreme pressure and at low temperatures they were able to transform a hydrogen sample into a solid state—a discovery that has eluded scientists for over 80 years.
The team decided to keep the single sample they created in the diamond anvil cell—the apparatus used for the experiment—until their findings were published. After their research was released in Science, they planned on sending the sample to Argonne National Laboratory in Chicago where it could be further studied.
However, before shipping the sample, the researchers decided to conduct a few more analyses. But a test to measure the pressure of the hydrogen went awry.
“We decided that before transporting [the sample] we should measure the pressure because we have specialized apparatus that they may not have,” Silvera said. “Four months earlier we had measured the pressure with a laser and it was fine…We again shined much less laser power into the sample and the diamonds instantaneously broke. We could hear it click. It’s not mysterious, it’s the way experiments end.”
Alexander Drozdov, a researcher at the Max Planck Institute for Chemistry in Germany, wrote in an email that “disappearing” samples are fairly common in the field.
“When you unload the cell and decrease pressure diamonds will be totally broken. Sometimes we can open the cell and observe just a lot of dust and no diamond at all. It is impossible to find any 10 microns sample in this heap of dust.”
After Silvera and Dias published their findings, several leading physicists questioned the sample's legitimacy. Eugene Gregoryanz, a high-pressure physicist at the University of Edinburgh in Scotland, wrote in an email that since the sample has lasted for so long—more than five months—it is an indication that is it not in fact solid hydrogen.
“If they had hydrogen as the sample it would have broke months and months before,” Gregoryanz wrote. “Since they kept it for 5-6 months demonstrates that it was not hydrogen—hydrogen at high pressures diffuses out within a day or two.”
Gregoryanz and Drozdov agreed that the experiment must be repeated to prove its validity. Silvera said he plans to attempt to replicate the experiment with a different type of diamond.
In response to the continued disputes over the validity of the findings, Silvera remains confident that the group did, however briefly, have the world’s only sample of solid metallic hydrogen.
“So the diamonds failed in our diamond cell. It could still be there, we just don’t know. Or it could’ve converted into a gas of molecular hydrogen. We just don’t know,” Silvera said.
—Staff writer Akshitha Ramachandran can be reached at firstname.lastname@example.org.