Adsorbate-induced formation of a surface-polarity-driven nonperiodic superstructure

TL;DR

This study demonstrates how hydrogen adsorption induces a nonperiodic, surface-polarity-driven superstructure on PdCrO2, revealing new electronic properties and potential for localized electronic states on inhomogeneous surfaces.

Contribution

It presents the first observation of a nonperiodic tiling structure caused by adsorbates on a frustrated antiferromagnet surface, linking surface polarity to superstructure formation.

Findings

Hydrogen adsorption creates a nonperiodic tiling superstructure.

Surface electronic properties are modified by adsorption, indicating electron localization.

Large terraces contain few-atom hexagonally packed domains.

Abstract

The chemical and electronic properties of surfaces and interfaces are important for many technologically relevant processes, be it in information processing, where interfacial electronic properties are crucial for device performance, or in catalytic processes, which depend on the types and densities of active nucleation sites for chemical reactions. Quasi-periodic and nonperiodic crystalline surfaces offer new opportunities because of their inherent inhomogeneity, resulting in localisation and properties vastly different from those of surfaces described by conventional Bravais lattices. Here, we demonstrate the formation of a nonperiodic tiling structure on the surface of the frustrated antiferromagnet PdCrO2 due to hydrogen adsorption. The tiling structure exhibits no long-range periodicity but comprises few-atom hexagonally packed domains covering large terraces. Measurement of the local density of states by tunnelling spectroscopy reveals adsorption-driven modifications to the quasi-2D electronic structure of the surface layer, showing exciting opportunities arising from electron localisation.