# Comment on "Spin-Orbit Coupling Induced Gap in Graphene on Pt(111) with Intercalated Pb Monolayer"

## TL;DR

This paper critically examines a recent study claiming a spin-orbit induced gap and quantum spin Hall state in graphene on Pb/Pt(111), highlighting the need for more careful data analysis and interpretation.

## Contribution

The authors provide a critical analysis questioning the original claims of spin-orbit effects and quantum spin Hall state in the studied graphene system.

## Key findings

- Original data interpretations are questionable.
- Further experiments are needed for definitive conclusions.
- Systematic analysis challenges previous claims.

## Abstract

Recently a paper of Klimovskikh et al. was published presenting experimental and theoretical analysis of the graphene/Pb/Pt(111) system. The authors investigate the crystallographic and electronic structure of this graphene-based system by means of LEED, ARPES, and spin-resolved PES of the graphene $\pi$ states in the vicinity of the Dirac point of graphene. The authors of this paper demonstrate that an energy gap of approx. 200 meV is opened in the spectral function of graphene directly at the Dirac point of graphene and spin-splitting of 100 meV is detected for the upper part of the Dirac cone. On the basis of the spin-resolved photoelectron spectroscopy measurements of the region around the gap the authors claim that these splittings are of a spin-orbit nature and that the observed spin structure confirms the observation of the quantum spin Hall state in graphene, proposed in earlier theoretical works. Here we will show that careful systematic analysis of the experimental data presented in this manuscript is needed and their interpretation require more critical consideration for making such conclusions. Our analysis demonstrates that the proposed effects and interpretations are questionable and require further more careful experiments.