Room temperature quantum spin Hall insulators with a buckled square lattice

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Physics

Background:

• Two-dimensional topological insulators (TIs), or quantum spin Hall (QSH) insulators, are crucial for spintronics due to robust edge states.
• Existing TIs primarily utilize hexagonal lattices, limiting material diversity.

Purpose of the Study:

• To explore the quantum spin Hall effect (QSHE) in a buckled square lattice.
• To predict and characterize a novel quasi-2D topological insulator material.

Main Methods:

• Global structure optimization to identify low-energy configurations.
• First-principles electronic structure calculations.
• Development of a tight-binding model for low-energy physics.

Main Results:

• Prediction of a stable, three-layer quasi-2D BiF structure with a large band gap (0.69 eV).
• Identification of this structure as a quantum spin Hall insulator.
• Demonstration of topological property robustness against substrate interaction (e.g., NaF).

Conclusions:

• The buckled square lattice hosts a QSHE, expanding the material base for topological insulators.
• The predicted quasi-2D BiF is a promising candidate for room-temperature spintronic applications.
• This work provides a new platform for engineering topological states.