MnBr$_2$ on the graphene on Ir(110) substrate: growth, structure, and super-moir\`e

TL;DR

This study explores the growth, structure, and super-moiré patterns of single-layer MnBr₂ on graphene supported by Ir(110), revealing a unique virtual moiré pattern resulting from complex lattice interactions.

Contribution

It uncovers the formation of a novel super-moiré pattern involving a virtual moiré of MnBr₂ with Ir(110), and analyzes its origin through experiments and ab initio calculations.

Findings

Growth morphology varies with temperature, from fractal to compact islands.

A super-moiré pattern arises from a three-lattice system involving MnBr₂, graphene, and Ir(110).

The virtual moiré is linked to inhomogeneous graphene binding to Ir(110).

Abstract

Single-layer MnBr$_2$ is grown on graphene (Gr) supported by Ir(110) and investigated using low-energy electron diffraction, scanning tunneling microscopy, and spectroscopy. The structure and epitaxial relationship with the substrate are systematically characterized. The structure and epitaxial relationship with the substrate are systematically characterized. The growth morphology strongly depends on the growth temperature, evolving from fractal to dendritic and eventually to compact dendritic skeletal islands, reflecting changes in the underlying surface diffusion processes. The pronounced variation in the apparent height with tunneling conditions for the magnetic insulator is explained based on the measured electronic density of states. MnBr$_2$ on Gr/Ir(110) constitutes a three-lattice system, giving rise to a super-moir\'e pattern -- a moir\'e of moir\'es. The super-moir\'e of MnBr$_2$/Gr/Ir(110) is unique, as it involves a virtual moir\'e of MnBr$_2$ with the Ir(110) surface lattice -- two lattices not in contact with each other. Using a careful Fourier analysis, the known properties of Gr/Ir(110), and the results of ab initio calculations, the origin of the virtual moir\'e is uncovered and related to the inhomogeneous binding of Gr to Ir(110). Comparative experiments with MnBr$_2$ on Gr/Ir(111) show similar growth and structure, but highlight the unique properties of the MnBr$_2$/Gr/Ir(110) super-moir\'e.