January 30, 2017

Metallic Hydrogen update

Thomas D. Cabot Professor of the Natural Sciences Isaac Silvera and postdoctoral fellow Ranga Dias have long sought the material, called atomic metallic hydrogen. In addition to helping scientists answer some fundamental questions about the nature of matter, the material is theorized to have a wide range of applications, including as a room-temperature superconductor.

“This is the Holy Grail of high-pressure physics,” Silvera said of the quest to find the material. “It’s the first-ever sample of metallic hydrogen on Earth, so when you’re looking at it, you’re looking at something that’s never existed before.”

In their experiments, Silvera and Dias squeezed a tiny hydrogen sample at 495 gigapascal (GPa), or more than 71.7 million pounds per square inch, which is greater than the pressure at the center of the Earth. At such extreme pressures, Silvera explained, solid molecular hydrogen, which consists of molecules on the lattice sites of the solid, breaks down, and the tightly bound molecules dissociate to transforms into atomic hydrogen, which is a metal.

While the work creates an important window into understanding the general properties of hydrogen, it also offers tantalizing hints at potentially revolutionary new materials.

Nextbigfuture covered earlier reports on the metallic hydrogen work back in November of 2016

Nextbigfuture noted that the main game changing aspect would be if the metallic hydrogen has indeed been confirmed to have been created and if it is found to be a room temperature superconductor and if it remains stable as a room temperature superconductor when it is removed from high pressure.

At this time the sample has not been reported to have been removed from high pressure and has not had confirmation as a room temperature superconductor

This manuscript first appeared on the arXiv preprint server in October 2016, and a revised version was subsequently published in the journal Science in January 2017

Shortly after the claim was published in Science, Nature's news division published an article stating that some other physicists regarded the result with skepticism. The diamond anvil used by the experimenters has an alumina coating to prevent breakages. It has been pointed out that the reflectivity of the sample at high pressure could be due to this coating. The imprecise and limited way in which this pressure was measured was also criticized.

Silvera stated that they did not repeat their experiment since doing more tests could damage or destroy their existing sample, but assured the scientific community that more tests are coming

“One prediction that’s very important is metallic hydrogen is predicted to be meta-stable,” Silvera said. “That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remain diamonds when that pressure and heat are removed.”

Understanding whether the material is stable is important, Silvera said, because predictions suggest metallic hydrogen could act as a superconductor at room temperatures.

“As much as 15 percent of energy is lost to dissipation during transmission,” he said, “so if you could make wires from this material and use them in the electrical grid, it could change that story.”

A room temperature superconductor, Dias said, could change our transportation system, making magnetic levitation of high-speed trains possible, as well as making electric cars more efficient and improving the performance of many electronic devices. The material could also provide major improvements in energy production and storage. Because superconductors have zero resistance, superconducting coils could be used to store excess energy, which could then be used whenever it is needed.

Metallic hydrogen could also play a key role in helping humans explore the far reaches of space, as a more powerful rocket propellant.

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