A First-order Phase Transition to Metallic Hydrogen

TL;DR

This paper reports experimental evidence of a first-order phase transition in hydrogen from insulator to metal at high pressures and temperatures, supporting theoretical predictions of a liquid atomic metallic phase.

Contribution

First experimental observation of a first-order insulator-metal transition in hydrogen at high pressures and temperatures, confirming theoretical plasma phase transition models.

Findings

Observation of a phase transition with changes in transmittance and reflectance.

Transition line has a negative slope, consistent with plasma phase transition theories.

Experimental data supports the existence of a liquid atomic metallic phase in hydrogen.

Abstract

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. The phase line of this transition has a negative slope in agreement with theories of the so-called plasma phase transition.