Metallization of hydrogen

TL;DR

This study investigates the metallization of hydrogen in phase III, demonstrating a transition from semiconducting to metallic behavior around 315 GPa through electrical and Raman spectroscopy measurements.

Contribution

It provides detailed experimental evidence of hydrogen's metallization at high pressures and correlates electrical conductivity with Raman spectroscopy data.

Findings

Hydrogen becomes metallic at approximately 315 GPa.

Electrical conductivity increases significantly at the transition.

Raman signal decreases as hydrogen transitions to metallic phase.

Abstract

In previous work,1 we showed that hydrogen metallizes in phase III at temperatures below ~200 K and at pressures near ~350 GPa. Here, we perform a detailed study of electrical conductivity R(T) in phase III over a pressure range of 200-400 GPa and a temperature range of 80-300 K, and we show that hydrogen transforms from a semiconducting to a metallic state already at ~315 GPa. This transformation is also supported by Raman spectroscopy: the Raman signal intensity decreases with pressure in accordance with the appearance and increase of electrical conductivity. Moreover, the Raman and electrical measurements yield the same boundary between the hydrogen phases III and V.