Strain-tunable topological quantum phase transition in buckled honeycomb lattices

TL;DR

This study demonstrates how biaxial strain can tune the topological quantum phase transition and band gap in buckled honeycomb lattices like silicene, enhancing their potential for topological transistors.

Contribution

It reveals strain-dependent control of topological phases and critical electric fields in buckled honeycomb lattices, extending previous models with first-principles calculations.

Findings

Topological phase transition can be tuned by biaxial strain.

Band gap varies from 0.7 meV to 3.0 meV with strain.

Critical electric field strength can be significantly adjusted.

Abstract

Low-buckled silicene is a prototypical quantum spin Hall insulator with the topological quantum phase transition controlled by an out-of-plane electric field. We show that this field-induced electronic transition can be further tuned by an in-plane hydrostatic biaxial strain $\varepsilon$, owing to the curvature-dependent spin-orbit coupling (SOC): There is a $Z_2$ = 1 topological insulator phase for biaxial strain $|\varepsilon|$ smaller than 0.07, and the band gap can be tuned from 0.7 meV for $\varepsilon = +0.07$ up to a fourfold 3.0 meV for $\varepsilon = -0.07$. First-principles calculations also show that the critical field strength $E_c$ can be tuned by more than 113\%, with the absolute values nearly 10 times stronger than the theoretical predictions based on a tight-binding model. The buckling structure of the honeycomb lattice thus enhances the tunability of both the quantum phase transition and the SOC-induced band gap, which are crucial for the design of topological field-effect transistors based on two-dimensional materials.