Supersolid state of matter

Area of Science:

• Condensed Matter Physics
• Quantum Materials

Background:

• Superfluidity is a quantum mechanical phenomenon observed in fluids.
• The possibility of supersolid states, exhibiting both superfluidity and crystalline order, has been a subject of intense research.
• Defects in crystalline solids, such as vacancies and interstitials, are known to influence material properties.

Purpose of the Study:

• To establish a necessary condition for a solid to exhibit superfluidity.
• To investigate the role of zero-point defects in the ground state of solids.
• To re-evaluate experimental observations of potential supersolid behavior in 4He.

Main Methods:

• Theoretical analysis of ground state properties of solids.
• Application of symmetry principles to defect structures.
• Interpretation of experimental data from recent 4He experiments.

Main Results:

• A necessary condition for solid superfluidity is the presence of zero-point vacancies, interstitial atoms, or both in the ground state.
• In the absence of symmetry between vacancies and interstitials, commensurate solids breaking continuous translation symmetry have zero probability of superfluidity.
• The bulk supersolid interpretation of recent 4He experiments is questioned.

Conclusions:

• The presence and symmetry of zero-point defects are critical for solid superfluidity.
• Alternative explanations, such as superfluid interfaces, may account for observed phenomena in experiments like those with 4He.
• The findings provide a new theoretical framework for understanding supersolid states.