On the Lifetime of Metastable Metallic Hydrogen

TL;DR

This paper investigates the metastability and decay mechanisms of metallic hydrogen as pressure decreases, identifying the pressure range where it remains long-lived and explaining the underlying physical reasons.

Contribution

It provides a theoretical analysis of the pressure-dependent lifetime of metallic hydrogen, highlighting the conditions for metastability and decay.

Findings

Metastable metallic hydrogen persists down to 10-20 GPa.

Decay occurs rapidly below 10 GPa due to nucleation of electron-free cavities.

Long-lived state is linked to the inability to form stable hydrogen molecules in high-density electron liquid.

Abstract

The molecular phase of hydrogen converts to the atomic metallic phase at high pressures estimated usually as 300 - 500 GPa. We analyze the decay of metallic phase as the pressure is relieved below the transition one. The metallic state is expected to be in the metastable long-lived state down to about 10 - 20 GPa and decays instantly at the lower pressures. The pressure range of the long-lived metastable state is directly associated with an impossibility to produce a stable hydrogen molecule immersed into the electron liquid of high density. For lower pressures, the nucleation of an electron-free cavity with the energetically favorable hydrogen molecule inside cannot be suppressed with the low ambient pressure.