Unconventional band structure via combined molecular orbital and lattice symmetries in a surface-confined metallated graphdiyne sheet

TL;DR

This study reveals an unconventional electronic band structure in metallated graphdiyne sheets on Ag(111), achieved through combined molecular orbital and lattice symmetries, with potential for designing novel 2D materials.

Contribution

It demonstrates the emergence of unique band structures in metallated GDY sheets using combined experimental and theoretical approaches, advancing 2D carbon material engineering.

Findings

Electronic band gap of 2.5 eV confirmed experimentally.

Observation of flat, Dirac, and Kagome bands near Fermi level.

Theoretical calculations support experimental results and predictions.

Abstract

Graphyne (GY) and graphdiyne (GDY)-based materials represent an intriguing class of two-dimensional (2D) carbon-rich networks with tunable structures and properties surpassing those of graphene. However, the challenge of fabricating atomically well-defined crystalline GY/GDY-based systems largely hinders detailed electronic structure characterizations. Here, we report the emergence of an unconventional band structure in mesoscopically regular (~1 {\mu}m) metallated GDY sheets featuring a honeycomb lattice on Ag(111) substrates. Employing complementary scanning tunnelling and angle-resolved photoemission spectroscopies, electronic band formation with a gap of 2.5 eV is rigorously determined in agreement with real-space electronic characteristics. Extensive density functional theory calculations corroborate our observations as well as recent theoretical predictions that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to Fermi level. These results illustrate the tremendous potential of engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon scaffolds.