Observation of the Wigner-Huntington Transition to Solid Metallic Hydrogen

TL;DR

This study reports the experimental observation of solid metallic hydrogen at extremely high pressures, demonstrating its metallic properties through reflectance measurements and theoretical modeling.

Contribution

First experimental evidence of solid metallic hydrogen produced in the laboratory at 495 GPa, with detailed optical and electronic property characterization.

Findings

Hydrogen becomes metallic at 495 GPa

Reflectance reaches 0.90 in visible spectrum

Plasma frequency of 30.1 eV indicating high electron density

Abstract

We have studied solid hydrogen under pressure at low temperatures. With increasing pressure we observe changes in the sample, going from transparent, to black, to a reflective metal, the latter studied at a pressure of 495 GPa. We have measured the reflectance as a function of wavelength in the visible spectrum finding values as high as 0.90 from the metallic hydrogen. We have fit the reflectance using a Drude free electron model to determine the plasma frequency of 30.1 eV at T= 5.5 K, with a corresponding electron carrier density of 6.7x1023 particles/cm3, consistent with theoretical estimates. The properties are those of a metal. Solid metallic hydrogen has been produced in the laboratory.