Semimetallic dense hydrogen above 260 GPa

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• Hydrogen's unique properties, including its potential for high-temperature superconductivity, are of significant scientific interest.
• Experimental reports on hydrogen metallization at high pressures have yielded conflicting results, necessitating further investigation.
• Advancements in theoretical and experimental techniques are crucial for understanding hydrogen's complex phase behavior.

Purpose of the Study:

• To reconcile conflicting experimental data regarding the metallic and superconducting states of hydrogen.
• To computationally determine the stable phase of hydrogen under high-pressure conditions.
• To investigate the potential for high-temperature superconductivity in metallic hydrogen.

Main Methods:

• Density Functional Theory (DFT) calculations.
• GW approximation for electronic structure.
• Phonon calculations to assess dynamic stability.
• Electron-phonon coupling analysis.

Main Results:

• The Cmca-12 phase is identified as the stable phase of hydrogen at ambient temperature and 260 GPa.
• Hydrogen transitions to a semimetallic state at 260 GPa in the Cmca-12 phase.
• Phonon calculations confirm the dynamic stability of the Cmca-12 phase.
• Calculated electron-phonon coupling is weak, indicating a low likelihood of high-temperature superconductivity.

Conclusions:

• The Cmca-12 phase explains the observed semimetallic behavior of hydrogen at high pressures.
• The study provides a theoretical framework to reconcile conflicting experimental findings.
• Hydrogen in the Cmca-12 phase is unlikely to be a high-temperature superconductor due to weak electron-phonon coupling.