Plumbene on a magnetic substrate: a combined STM and DFT study

TL;DR

This study combines STM experiments and DFT calculations to investigate plumbene on a magnetic substrate, revealing its structural, electronic, and topological properties, including a transition from quantum spin Hall to quantum anomalous Hall states.

Contribution

It provides the first combined experimental and theoretical analysis of plumbene on a magnetic substrate, highlighting the effects of hybridization and spin-orbit coupling on its topological phases.

Findings

Pb forms a flat honeycomb lattice on Fe/Ir(111)

Spin-orbit interaction causes Dirac cone splitting in unoccupied states

Hybridization induces a transition from quantum spin Hall to quantum anomalous Hall state

Abstract

As heavy analog of graphene, plumbene is a two-dimensional material with strong spin-orbit coupling effects. Using scanning tunneling microscopy (STM), we observe that Pb forms a flat honeycomb lattice on an Fe monolayer on Ir(111). In contrast, without the Fe layer, a c(2x4) structure of Pb on Ir(111) is found. We use density functional theory (DFT) calculations to rationalize these findings and analyze the impact of the hybridization on the plumbene band structure. In the unoccupied states the splitting of the Dirac cone by spin-orbit interaction is clearly observed while in the occupied states of the freestanding plumbene we find a band inversion that leads to the formation of a topologically non-trivial gap. Exchange splitting as mediated by the strong hybridization with the Fe layer drives a quantum spin Hall to quantum anomalous Hall state transition.