Partial Kekule Ordering of Adatoms on Graphene

TL;DR

This paper reveals that dilute adatoms on graphene can develop a hidden Kekule mosaic order due to electron-mediated interactions, leading to a spectral gap and altered transport properties at low temperatures.

Contribution

It demonstrates the emergence of a partial Kekule ordering of adatoms on graphene driven by electron interactions, a phenomenon not previously identified.

Findings

Adatoms tend to form a Kekule mosaic order on graphene.

The ordered state opens an electronic gap, affecting conductivity.

The transition occurs below a critical temperature.

Abstract

Electronic and transport properties of Graphene, a one-atom thick crystalline material, are sensitive to the presence of atoms adsorbed on its surface. An ensemble of randomly positioned adatoms, each serving as a scattering center, leads to the Bolzmann-Drude diffusion of charge determining the resistivity of the material. An important question, however, is whether the distribution of adatoms is always genuinely random. In this Article we demonstrate that a dilute adatoms on graphene may have a tendency towards a spatially correlated state with a hidden Kekule mosaic order. This effect emerges from the interaction between the adatoms mediated by the Friedel oscillations of the electron density in graphene. The onset of the ordered state, as the system is cooled below the critical temperature, is accompanied by the opening of a gap in the electronic spectrum of the material, dramatically changing its transport properties.