Harvard, Boston, Massachusetts. Ranga Dias and Isaac Silvera compressed hydrogen between two diamonds at 495 GPa at -268°C, claiming to have created metallic hydrogen. Metallic hydrogen is thought to be superfluid and superconductive, and five times more efficient than liquid hydrogen as a propellant. The two Harvard scientists believe they have produced metallic hydrogen (like that believed to be present deep inside Jupiter, for example). Their feat, which has eluded physicists for more than 80 years, would mark a huge leap forward in high-pressure physics, not only because it demonstrates a new fundamental property of the most abundant element in the universe, but because the metallic form is predicted to remain a superconductor at room temperature. If this turns out to be true, and an efficient means of producing it can be devised, applied uses for metallic hydrogen could include superconductors and space travel. However, several doubts have subsequently arisen, even from the two scientists themselves: it is not at all clear whether the shiny material the researchers see is actually hydrogen; it could be alumina (aluminum oxide), which coats the diamond tips in the anvil and could behave differently under pressure. In June 2019, however, a team from the CEA (Commission for Atomic Energy and Alternative Energies) claimed to have created metallic hydrogen at approximately 425 GPa using a toroidal diamond anvil cell produced using electron beam machining.
