Visualizing the Localized Electrons of a Kagome Flat Band

Abstract

Destructive interference between electron wavefunctions on the two-dimensional (2D) kagome lattice induces an electronic flat band, which could host a variety of interesting many-body quantum states. Key to realize these proposals is to demonstrate the real space localization of kagome flat band electrons. In particular, the extent to which the often more complex lattice structure and orbital composition of realistic materials counteract the localizing effect of destructive interference, described by the 2D kagome lattice model, is hitherto unknown. We used scanning tunneling microscopy (STM) to visualize the non-trivial Wannier states of a kagome flat band at the surface of CoSn, a kagome metal. We find that the local density of states associated with the flat bands of CoSn is localized at the center of the kagome lattice, consistent with theoretical expectations for their corresponding Wannier states. Our results show that these states exhibit an extremely small localization length of two to three angstroms concomitant with a strongly renormalized quasiparticle velocity, which is comparable to that of moiré superlattices. Hence, interaction effects in the flat bands of CoSn could be much more significant than previously thought. Our findings provide fundamental insight into the electronic properties of kagome metals and are a key step for future research on emergent many-body states in transition metal based kagome materials.

References in corpus (8)

• High temperature fractional quantum Hall states
• Fractional quantum Hall states at zero magnetic field
• Nearly-flat bands with nontrivial topology
• Negative flat band magnetism in a spin-orbit coupled correlated kagome magnet
• One-dimensional Topological Edge States of Bismuth Bilayers
• Fantastic flat bands and where to find them: The CoSn-type compounds
• Tuning the flat bands of the kagome metal CoSn with Fe, In, or Ni doping
• Observation of backscattering induced by magnetism in a topological edge state

Cited by in corpus (6)

• Flat-Band Lasing in Silicon Waveguide-Integrated Metasurfaces
• FeGe as a building block for the kagome 1:1, 1:6:6, and 1:3:5 families: hidden d-orbital decoupling of flat band sectors, effective models and interaction Hamiltonians
• Kagome metals
• Tuning electronic pairing by uniaxial strain in kagome lattices
• Frustration-free free fermions
• High-pressure modulation of breathing kagome lattice: Cascade of Lifshitz transitions and evolution of the electronic structure