Structural approach to charge density waves in low-dimensional systems: electronic instability and chemical bonding

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Chemistry

Background:

• Charge density wave (CDW) instability is a phenomenon in low-dimensional metals with unclear fundamental mechanisms.
• Recent discovery of novel 2D and 3D CDW materials necessitates re-evaluation of existing theories.
• The electron-hole instability theory, established over 50 years ago for quasi-1D conductors, requires updating.

Purpose of the Study:

• To revisit fundamental concepts of CDW instability across various material dimensions.
• To emphasize the role of momentum-dependent electron-phonon coupling in CDW formation.
• To explore the interplay between electronic, structural, and chemical bonding aspects in CDW materials.

Main Methods:

• Analysis of a diverse range of CDW materials.
• Revisiting established theoretical frameworks for CDW instability.
• Integrating first-principles calculations with chemical bonding principles.

Main Results:

• For quasi-1D systems, weak coupling theories and Fermi surface nesting adequately explain CDW energy gain.
• In higher-dimensional materials, intermediate and strong coupling regimes dominate.
• Periodic lattice distortion (PLD) significantly modifies chemical bonding, driving instability in higher dimensions.

Conclusions:

• The mechanism of CDW instability varies with material dimensionality.
• A microscopic approach combining condensed matter physics and chemical bonding is crucial for understanding CDWs.
• Future research should focus on the detailed interplay of electronic structure, lattice dynamics, and chemical bonding.