Quantum spin Hall effect in two-dimensional hydrogenated SnPb alloy films

Area of Science:

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

Background:

• Topological insulators (TIs) are materials with unique electronic properties.
• Understanding the factors that induce topological phases is crucial for materials design.

Purpose of the Study:

• To investigate the topological properties of hydrogenated tin-lead (SnPb) alloy films.
• To establish criteria for the transition between normal band insulators (NI) and topological insulators (TIs) in these materials.

Main Methods:

• First-principles calculations were employed to study geometric and band structures.
• Analysis included band inversion, helical edge states, and spin-orbit coupling (SOC) effects.

Main Results:

• Twenty configurations of buckled hydrogenated SnPb alloy (SnxPb8-xH8) films were analyzed.
• Topological insulator phases were identified for SnxPb8-xH8 with x ≥ 1.
• The band gap increased from 0.087 eV to 0.98 eV as x increased from 1 to 7.
• Lead (Pb) atoms contribute significantly to spin-orbit coupling (SOC), driving the topological transition.

Conclusions:

• A critical Pb:Sn atomic ratio greater than 1/12 is sufficient to induce a topological phase transition.
• The findings provide a design rule for hydrogenated SnPb alloy films as topological insulators.
• This research offers a reference for developing novel topological devices based on NI-TI heterojunctions.