A First-order Phase Transition to Metallic Hydrogen

Understand

The insulator-metal transition in hydrogen is one of the most outstanding problems in condensed matter physics.

• The high-pressure metallic phase is now predicted to be liquid atomic from T=0 K to very high temperatures.
• We have conducted measurements of optical properties of hot dense hydrogen in the region of 1.1-1.7 Mbar and up to 2200 K.
• We observe a first-order phase transition accompanied by changes in transmittance and reflectance characteristic of a metal.