Periodic arrays of intercalated atoms in twisted bilayer graphene: an \it{ ab initio} investigation

TL;DR

This study uses ab initio methods to explore how transition metals like Mo and Ru intercalate in twisted bilayer graphene, revealing their potential to form quasi-periodic arrays and affect magnetic properties, with observable STM signatures.

Contribution

It provides the first ab initio analysis of transition metal intercalation in twisted bilayer graphene, highlighting the formation of quasi-periodic arrays and their magnetic and electronic effects.

Findings

Mo and Ru can form quasi-periodic arrays due to layer misalignment.

Intercalation can quench or modify magnetic moments of TMs.

Intercalated TMs produce identifiable STM bright spots.

Abstract

We have performed an \it {ab initio} investigation of transition metals (TMs = Mo, Ru, Co, and Pt) embedded in twisted bilayer graphene (tBG) layers. Our total energy results reveal that, triggered by the misalignment between the graphene layers, Mo and Ru atoms may form a quasi-periodic (triangular) array of intercalated atoms. In contrast, the formation of those structures is not expected for the other TMs, Co and Pt atoms. The net magnetic moment (m) of Mo and Ru atoms may be quenched upon intercalation, depending on the stacking region (AA or AB). For instance, we find a magnetic moment of 0.3 $\mu_{\rm B}$ (1.8 $\mu_{\rm B}$) for Ru atoms intercalated between the AA (AB) regions of the stacked twisted layers. Through simulated scanning tunneling microscopy (STM) images, we verify that the presence of intercalated TMs can be identified by the formation of bright (hexagonal) spots lying on the graphene surface.