Metallic hydrogen observed for the first time

The existence of metal-phase hydrogen was predicted more than 80 years ago, sparking a race to observe it. While there have been many claims of proof in recent years, none have managed to convince the scientific community. Now, a French team working at the SOLEIL synchrotron facility have published a paper in Nature suggesting they have done just that.

The team report that the development of a new kind of diamond anvil cell that can exert over 4 million times the Earth's atmospheric pressure, together with the non-intrusive measurement of the insulator-metal transformation using very bright infrared radiation produced by the synchrotron allowed the researchers to observe the transition to the metallic phase. 

Paul Dumas, Emeritus Research Director at the The French National Center for Scientific Research, on secondment at the Synchrotron SOLEIL facility, said: “Far from closing the case on a fundamental question that has fascinated scientists since it was first posited decades ago, this observation paves the way for many exciting possibilities. To begin with, it will be used to establish a benchmark for validating theoretical approaches to calculating the properties of very dense hydrogen at the centre of giant planets, or for nuclear fusion by inertial confinement fusion.” 

The simplicity of hydrogen (the first atom in the Periodic Table, made up of one proton and one electron) has played a key role in the development of modern physics. At the beginning of the 20th century, Quantum Mechanics led us to understand the properties of the hydrogen atom, and then of the dihydrogen molecule (H2). However, producing an accurate description of its behavior under pressure that would provide data on the hydrogen phase diagram, in other words, knowledge of the hydrogen state at different pressure and temperature levels, entails extremely complex computations and experiments. The data obtained are a world first and will be used to advance theoretical models.