Towards Topological Quasi-Freestanding Stanene via Substrate Engineering

TL;DR

This paper explores substrate engineering, specifically buffer layers, to achieve quasi-freestanding stanene that exhibits quantum spin Hall effect at room temperature, combining theoretical insights with initial experimental attempts.

Contribution

It introduces a detailed density functional theory analysis of buffer layers to optimize QSHE in stanene and reports the first experimental growth on SiC(0001).

Findings

Buffer layers can decouple stanene from substrates, preserving QSHE.

Theoretical models predict enhanced QSHE stability with buffer layers.

Initial experimental growth of buffer layers on SiC(0001) was successful.

Abstract

In search for a new generation of spintronics hardware, material candidates for room temperature quantum spin Hall effect (QSHE) have become a contemporary focus of investigation. Inspired by the original proposal for QSHE in graphene, several heterostructures have been synthesized, aiming at a hexagonal monolayer of heavier group IV elements in order to promote the QSHE bulk gap via increased spin-orbit coupling. So far, however, the monolayer/substrate coupling, which can manifest itself in strain, deformation, and hybridization, has proven to be detrimental to the aspired QSHE conditions for the monolayer. Specifically focusing on stanene, the Sn analogue of graphene, we investigate how an interposing buffer layer mediates between monolayer and substrate in order to optimize the QSHE setting. From a detailed density functional theory study, we highlight the principal mechanisms induced by such a buffer layer to accomplish quasi-free standing stanene in its QSHE phase. We complement our theoretical predictions by presenting the first real attempts to grow a buffer layer on SiC(0001) on which stanene can be deposited.