The Melting Line of Hydrogen at High Pressures

TL;DR

This paper reports a novel experimental approach to measure the melting line of solid hydrogen at high pressures, identifying a peak that may indicate the insulator-to-metal transition, a key step toward understanding hydrogen's metallization.

Contribution

The study introduces a pulsed laser heating technique to accurately measure hydrogen's melting line at high pressures, overcoming previous experimental limitations.

Findings

Melting line peak at 64.7 GPa and 1055 K

First direct measurement of hydrogen melting curve at these pressures

Potential precursor to hydrogen metallization

Abstract

The insulator to metal transition in solid hydrogen was predicted over 70 years ago but the demonstration of this transition remains a scientific challenge. In this regard, a peak in the temperature vs. pressure melting line of hydrogen may be a possible precursor for metallization. However, previous measurements of the fusion curve of hydrogen have been limited in pressure by diffusion of hydrogen into the gasket or diamonds. To overcome this limitation we have used an innovative technique of pulsed laser heating of the sample and final peak in the melting line at P=64.7+-4GPa and T=1055+-20 K.