Harvard scientists have created metallic hydrogen, one of the rarest and most potentially valuable materials in the world. At a pressure of 495 gigapascal (GPa) and temperature of -268 degree Celsius, they converted gaseous hydrogen into its metallic form, and they consider it as the Holy Grail of high-pressure physics. The reason why this creation is so phenomenal is because of its superconductivity at room temperatures.
The electrical conductors which we use in our homes have some amount of electrical resistance associated with them. The electric transmission wires for example dissipate so much energy as heat due to this resistance. This loss of power has been calculated to be as high as 30 percent over long distance transmission. So to avoid this power loss and create efficient transmission lines, developing room temperature superconductors has been a long standing focus of research. Superconductivity is the ability of a material to conduct electricity with zero resistance. Hitherto developed superconductors are applicable only at extremely negative temperatures. One of the highest temperatures at which superconductivity could be achieved is -150 degree Celsius for a Tl-Ba-Cu oxide, far below our environmental temperatures. Hence scientists have been working on developing materials that could possess superconductivity at room temperatures. Metallic hydrogen is said to possess this room temperature superconductivity and it could potentially revolutionise the environment around us.
In 1935, Eugene Wigner and Hillard Bell Huntington from Princeton University theoretically calculated that molecular hydrogen can be converted into metallic state at 25 GPa in their paper “On the Possibility of a Metallic Modification of Hydrogen”. But it was not possible to experimentally verify for long, as achieving such a high pressure of 25 GPa was almost impossible. With advances in science and accurate calculations, the theoretical pressure required for this transition kept increasing to between 400 and 500 GPa. Meanwhile in 1968, Neil Ashcroft, a British solid state physicist, stated that metallic hydrogen behaves as superconductor up to a temperature as high as 17 degree Celsius. It did not take long to couple these two facts and try to synthesise metallic hydrogen as a source of superconductivity.
Harvard scientists Isaac Silvera and postdoctoral fellow Ranga Dias have created metallic hydrogen in their lab. They compressed hydrogen sample at 495 GPa between two polished tips of diamond anvil. The compressed solid hydrogen was initially transparent at low temperatures. With increase in pressure, the specimen turned more dark and opaque. As the pressure reached 495 GPa, it became shiny and reflective, indicating that it has transformed itself into a metal. It is said that metallic hydrogen is metastable, which means that it will retain its property even after removing the compression.
If the created metal proves to be what it is expected to be, then electric appliances and conductors will see tremendous change. Room temperature super conductors enable transfer of electricity across long distances without any loss of power. Magnetic levitation and high-speed trains are possible with considerably simpler infrastructure. It also holds the potential to become a very powerful rocket propellant. Tremendous amount of energy would be released when converting metallic hydrogen back to molecular hydrogen and that could be used to propel rockets.
But all these claims and applause do not come without criticism and scepticism. Researchers have expressed that the finding is not that convincing. There is just one specimen identified and tested for reflectivity at high pressure, to verify whether it is real metallic hydrogen. They state . Nevertheless, Harvard University confidently proclaims that it has made the first ever sample of metallic hydrogen on Earth.
Featured image source: Nextbigfuture, Video source: Harvard