Engineering topological surface states: HgS, HgSe, and HgTe

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Topological surface states (TSS) in materials like metacinnabar (β-HgS) exhibit unique electronic properties.
• Understanding the influence of surface termination and modification on these states is critical for device applications.

Purpose of the Study:

• To investigate the effects of surface termination and chemical modification on the protected surface states of β-HgS.
• To analyze how surface dangling bonds and passivation influence the Dirac cone properties.
• To determine the impact of surface modifications on the spatial localization of topological edge states.

Main Methods:

• Density functional electronic structure calculations were employed.
• Analysis focused on the (110) and (001) surfaces of β-HgS.
• Investigated the role of dangling bonds and surface passivation on topological states.

Main Results:

• The Dirac cone is isotropic on the (110) surface but highly anisotropic on the pure (001) surface.
• Surface passivation modifies Dirac cone anisotropy by incorporating contributions from dangling bonds.
• Surface modifications alter the depth and decay length of topologically protected edge states.

Conclusions:

• Surface termination and modification play a crucial role in defining the electronic properties of β-HgS surface states.
• Dangling bonds on HgX surfaces (X=S, Se, Te) directly impact Dirac cone characteristics.
• The spatial localization of edge states is sensitive to surface treatments, essential for interpreting experimental data like photoemission spectroscopy.