Identifying Band Inversions in Topological Materials Using Diffusion Monte Carlo

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Physics

Background:

• Topological insulators possess insulating bulk and conducting surface states, with band inversion as a key characteristic.
• Spin-orbit coupling (SOC) is vital for topological properties, causing orbital character changes at band edges.
• Accurate many-body methods are needed to detect band inversion in correlated materials for spintronics and quantum computing.

Purpose of the Study:

• To develop a novel continuum quantum Monte Carlo (QMC) method for detecting band inversion.
• To accurately account for electron correlation and spin-orbit coupling (SOC) in topological insulators.
• To enable reliable prediction of band structures for correlated topological materials.

Main Methods:

• Developed a momentum-space-resolved atomic population analysis using the Löwdin method and diffusion Monte Carlo (DMC).
• Integrated the method into the QMCPACK ab initio QMC package.
• Applied the technique to bismuth telluride (Bi2Te3) and its monolayer, bilayer, and bulk forms.

Main Results:

• Demonstrated band inversion between Bi-p and Te-p states at the Γ-point in bismuth telluride.
• Observed changes in orbital charge distribution (increased on Bi-p, decreased on Te-p) due to SOC.
• Quantified differences in band inversion for monolayer versus bilayer and bulk Bi2Te3.

Conclusions:

• The novel QMC method reliably detects band inversion in topological insulators.
• This approach enhances the understanding of correlation and topology interplay in materials.
• Facilitates future many-body studies for discovering novel topological materials.