Metallization of Fluid Hydrogen

TL;DR

This study measures the electrical resistivity of liquid hydrogen under high pressures and temperatures, revealing a transition from semiconducting to metallic fluid, with implications for understanding hydrogen's metallization process.

Contribution

It provides experimental data on hydrogen's resistivity at extreme conditions, highlighting a continuous transition to a metallic state and discussing possible underlying mechanisms.

Findings

Hydrogen becomes metallic at 140 GPa and 3000 K.

Resistivity reaches 500 micro-ohm-cm, similar to liquid metals.

The transition involves complex pairing and structural factors.

Abstract

The electrical resistivity of liquid hydrogen has been measured at the high dynamic pressures, densities and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) processes in which structural changes are paramount.