Metastable solid ⁴He and the possible role of point defects.

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Low-Temperature Physics

Background:

• Solid helium-4 exhibits a metastable phase.
• Point defects are hypothesized to play a role in destabilizing this phase.

Purpose of the Study:

• Investigate the role of point defects in the destabilization of solid helium-4's metastable phase.
• Determine the formation energies of vacancies and interstitials in solid helium-4.

Main Methods:

• Utilized a trial function of the shadow class with an explicit symmetrical kernel.
• This function allows for effective atom exchange and delocalization of atoms and defects.

Main Results:

• Calculated zero formation energy for vacancies at a critical pressure (Pc) of 20 ± 2 atm, aligning with experimental findings.
• Identified the pressure at which self-interstitials also exhibit zero formation energy.
• Estimated formation energies for helium-3 interstitials and substitutional impurities.

Conclusions:

• Point defects, particularly vacancies, are crucial for understanding the destabilization of the metastable phase of solid helium-4.
• The theoretical framework provides accurate predictions for defect behavior in solid helium-4.
• The study offers valuable insights into the properties of quantum systems with defects.