Strain-induced large band-gap topological insulator in a new stable silicon allotrope: dumbbell silicene

TL;DR

This study predicts that applying strain to a new silicon allotrope called dumbbell silicene induces a topological insulator phase with a large band gap, promising for room-temperature spintronics and silicon-based electronics.

Contribution

It demonstrates strain-induced topological phase transition in dumbbell silicene and identifies optimal conditions for large band gaps suitable for practical applications.

Findings

Maximum topological band gap of 12 meV under isotropic strain

Enhanced band gap of 36 meV with anisotropic strain

BN sheet as an ideal substrate maintaining nontrivial topology

Abstract

By the generalized gradient approximation in framewok of density functional theory, we investigate a 2D topological insulator of new silicon allotrope (call dumbbell silicene synthesized recently by Cahangirov et al) through tuning external compression strain, and find a topological quantum phase transition from normal to topological insulator, i.e., the dumbbell silicene can turn a two-dimensional topological insulator with an inverted band gap. The obtained maximum topological nontrivial band gap about 12 meV under isotropic strain is much larger than that for previous silicene, and can be further improved to 36 meV by tuning anisotropic strain, which is sufficiently large to realize quantum spin Hall effect even at room-temperature, and thus is beneficial to the fabrication of high-speed spintronics devices. Furthermore, we confirm that the boron nitride sheet is an ideal substrate for the experimental realization of the dumbbell silicene under external strain, maintaining its nontrivial topology. These properties make the two-dimensional dumbbell silicene a good platform to study novel quantum states of matter, showing great potential for future applications in modern silicon-based microelectronics industry.