The electronic structure of intertwined kagome, honeycomb, and triangular sublattices of the intermetallics MCo$_2$Al$_9$

TL;DR

This study uncovers Dirac-like electronic dispersions in intermetallic MCo$_2$Al$_9$ compounds, revealing their potential as platforms for topological physics due to hidden symmetries and spin-orbit coupling effects.

Contribution

First experimental characterization of the electronic structure of MCo$_2$Al$_9$, identifying Dirac-like states from hidden lattice symmetries and analyzing spin-orbit coupling effects.

Findings

Discovery of Dirac-like dispersions from hidden kagome and honeycomb symmetries.

Observation of spin-orbit coupling-induced energy gaps.

Proposal of MCo$_2$Al$_9$ as a candidate for topological phenomena.

Abstract

Intermetallics are an important playground to stabilize a large variety of physical phenomena, arising from their complex crystal structure. The ease of their chemical tuneabilty makes them suitable platforms to realize targeted electronic properties starting from the symmetries hidden in their unit cell. Here, we investigate the family of the recently discovered intermetallics MCo$_2$Al$_9$ (M: Sr, Ba) and we unveil their electronic structure for the first time. By using angle-resolved photoelectron spectroscopy and density functional theory calculations, we discover the existence of Dirac-like dispersions as ubiquitous features in this family, coming from the hidden kagome and honeycomb symmetries embedded in the unit cell. Finally, from calculations, we expect that the spin-orbit coupling is responsible for opening energy gaps in the electronic structure spectrum, which also affects the majority of the observed Dirac-like states. Our study constitutes the first experimental observation of the electronic structure of MCo$_2$Al$_9$ and proposes these systems as hosts of Dirac-like physics with intrinsic spin-orbit coupling. The latter effect suggests MCo$_2$Al$_9$ as a future platform for investigating the emergence of non-trivial topology.