Statistical mechanics of vacancy and interstitial strings in hexagonal columnar crystals

Area of Science:

• Condensed matter physics
• Statistical mechanics

Background:

• Columnar crystals exhibit defects such as vacancy-interstitial loops and strings.
• These defect strings are influenced by the columnar lattice and can alter their size and shape.

Purpose of the Study:

• To analyze the size, shape distribution, and volume fraction of defect strings using a directed living polymer model.
• To investigate the string proliferation transition leading to a supersolid phase.
• To calculate the line tension of various defects in a triangular lattice.

Main Methods:

• Analysis using directed living polymers framework.
• Estimation of wandering entropy and examination of transition regime behavior.
• Numerical calculation of line tension for different defect types and interaction potentials.

Main Results:

• The centered interstitial defect exhibits the lowest energy across a broad range of interactions.
• The symmetric vacancy is favored only for very short interaction ranges.
• String proliferation transition is linked to transverse fluctuations overcoming string line tension.

Conclusions:

• Defect strings in columnar crystals can be effectively modeled as directed living polymers.
• The study provides insights into the formation of supersolid phases driven by defect dynamics.
• Understanding defect line tension is crucial for predicting crystal phase behavior.