Can the quantum spin Hall state of silicene be preserved on substrate

TL;DR

This paper proposes a novel sandwich structure to preserve the quantum spin Hall state of silicene on substrates, overcoming substrate-induced phase transition issues that hinder silicene's electronic applications.

Contribution

It introduces a protective sandwich structure to maintain silicene's topological properties, validated by first-principles calculations of edge states and Z2 invariant.

Findings

Sandwich structure preserves QSHE in silicene on substrates.

Substrate effect can be mitigated by inverse symmetrical design.

Demonstrated with CeO2 and CaF2 based structures.

Abstract

The substrate-induced topological phase transition of silience is a formidable obstacle for developing silicene-based materials and devices for compatibility with current electronics by using its topologically protected dissipationless edge states. First-principles calculations indicate that the substrate will result in a phase transition from topological nontrivial phase to trivial phase of silicene, although its Dirac cone is still obvious. The substrate effect (equivalent to an electric field) annihilates its spin-orbit coupling effect, the reason why its quantum spin Hall effect (QSHE) of silicene has not been experimentally observed. Unfortunately, external electric field seems impossible to recover the QSHE due to the screen effect of substrate. We here first propose a viable strategy (constructing inverse symmetrical sandwich structure (protective layer/silicene/substrate)) to preserve quantum spin Hall (QSH) state of silicene, which is demonstrated by using two representatives (CeO2(111)/silicene/CeO2(111) and CaF2(111)/silicene/CaF2(111)) through the calculated edge states and Z2 invariant. This work takes a critical step towards fundamental physics and realistic applications of silicene-based nanoelectronic devices.