Electron-phonon coupling and the metallization of solid helium at terapascal pressures

Area of Science:

• Condensed Matter Physics
• Materials Science under Extreme Conditions
• Computational Physics

Background:

• Solid Helium exhibits unique quantum behaviors under high pressure and temperature.
• Understanding its electronic properties is crucial for astrophysics, particularly white dwarf cooling.

Purpose of the Study:

• To investigate the anharmonic vibrational properties of solid Helium.
• To accurately calculate the electron-phonon coupling and its effect on the electronic band gap.
• To determine the metallization pressure of Helium at 0 K.

Main Methods:

• Utilized first-principles methods for calculations.
• Employed a self-consistent field framework for anharmonic vibrational properties.
• Applied a nonperturbative approach for electron-phonon coupling.

Main Results:

• Calculated internal/free energies, density-pressure relation, stress tensor, and thermal expansion.
• Found a metallization pressure of 32.9 TPa at 0 K, higher than previously reported.
• Quantified significant band gap increases due to electron-phonon coupling (2.8 eV) and thermal expansion (0.1 eV) at 30 TPa.

Conclusions:

• Accurate electron-phonon coupling requires nonperturbative methods.
• Vibrational effects substantially renormalize the electronic band gap of solid Helium.
• The calculated metallization pressure has implications for astrophysical models of white dwarf cooling.