Robust topological nodal lines in halide carbides.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Topological nodal line semimetals exhibit unique electronic properties with gapless states forming a closed 1D Fermi surface.
• These materials are of significant interest for fundamental physics and potential applications in quantum technologies.

Purpose of the Study:

• To theoretically predict a new material exhibiting topological nodal line semimetal properties.
• To identify the protective symmetries and topological invariants associated with the nodal lines.
• To explore the potential of this material for realizing functional topological devices.

Main Methods:

• Theoretical prediction of material properties.
• Analysis of electronic band structure.
• Identification of crystalline symmetries and topological invariants (mirror Chern numbers).

Main Results:

• Y2C2I2 is predicted to be a novel metal with interconnected nodal lines.
• The nodal lines are protected by parallel mirror planes (kz = 0 and kz = 0.5).
• The material exhibits independent mirror Chern numbers |μ1| = |μ| = 1, confirming its topological nature.
• Interlocking 2D nodal lines along the c-axis lead to robust topological properties in both 3D and 2D forms.

Conclusions:

• Y2C2I2 is a promising candidate for a topological chain metal and a topological nodal line material.
• Its size-independent topological properties make it suitable for developing functional topological devices.
• Layered halide carbides represent a new class of materials for topological electronics.