Magnetic-coupled electronic landscape in bilayer-distorted titanium-based kagome metals

TL;DR

This study uncovers the unique electronic structure of bilayer-distorted kagome metals $ extit{Ln}$Ti${_3}$Bi${_4}$, revealing flat bands, van Hove singularities, and magnetic band splitting, highlighting their potential for novel quantum phases.

Contribution

It provides the first detailed experimental and theoretical analysis of the electronic structure of bilayer-distorted kagome metals $ extit{Ln}$Ti${_3}$Bi${_4}$, including magnetic effects.

Findings

Discovery of double flat bands and multiple van Hove singularities.

Observation of magnetic band splitting in NdTi${_3}$Bi${_4}$.

Identification of unique electronic features due to lattice distortion.

Abstract

Quantum materials whose atoms are arranged on a lattice of corner-sharing triangles, $\textit{i.e.}$, the kagome lattice, have recently emerged as a captivating platform for investigating exotic correlated and topological electronic phenomena. Here, we combine ultra-low temperature angle-resolved photoemission spectroscopy (ARPES) with scanning tunneling microscopy and density functional theory calculations to reveal the fascinating electronic structure of the bilayer-distorted kagome material $\textit{Ln}$Ti${_3}$Bi${_4}$, where $\textit{Ln}$ stands for Nd and Yb. Distinct from other kagome materials, $\textit{Ln}$Ti${_3}$Bi${_4}$ exhibits two-fold, rather than six-fold, symmetries, stemming from the distorted kagome lattice, which leads to a unique electronic structure. Combining experiment and theory we map out the electronic structure and discover double flat bands as well as multiple van Hove singularities (VHSs), with one VHS exhibiting higher-order characteristics near the Fermi level. Notably, in the magnetic version NdTi${_3}$Bi${_4}$, the ultra-low base temperature ARPES measurements unveil an unconventional band splitting in the band dispersions which is induced by the ferromagnetic ordering. These findings reveal the potential of bilayer-distorted kagome metals $\textit{Ln}$Ti${_3}$Bi${_4}$ as a promising platform for exploring novel emergent phases of matter at the intersection of strong correlation and magnetism.