Stabilizing an atomically thin quantum spin Hall insulator at ambient conditions: Graphene-intercalation of indenene

TL;DR

This paper demonstrates that intercalating indenene into epitaxial graphene stabilizes its quantum spin Hall insulator properties in ambient conditions, enabling practical device applications and ex-situ experiments.

Contribution

The study introduces a novel method of stabilizing indenene by intercalation into graphene, preserving its topological properties outside of controlled environments.

Findings

Indenene intercalation protects against oxidation.

Topological character remains intact after intercalation.

Enables ex-situ device fabrication and testing.

Abstract

Atomic monolayers on semiconductor surfaces represent a new class of functional quantum materials at the ultimate two-dimensional limit, ranging from superconductors [1, 2] to Mott insulators [3, 4] and ferroelectrics [5] to quantum spin Hall insulators (QSHI) [6, 7]. A case in point is the recently discovered QSHI indenene [7, 8], a triangular monolayer of indium epitaxially grown on SiC(0001), exhibiting a $\sim$120meV gap and substrate-matched monodomain growth on the technologically relevant $\mu$m scale [9]. Its suitability for room-temperature spintronics is countered, however, by the instability of pristine indenene in air, which destroys the system along with its topological character, nullifying hopes of ex-situ processing and device fabrication. Here we show how indenene intercalation into epitaxial graphene offers effective protection from the oxidizing environment, while it leaves the topological character fully intact. This opens an unprecedented realm of ex-situ experimental opportunities, bringing this monolayer QSHI within realistic reach of actual device fabrication and edge channel transport.