Acoustic Wave-Function Imaging of Sublattice Physics in a Kagome Lattice
The canonical kagome band structure hosts a Dirac cone, saddle-point van Hove singularities (vHS), and a flat band. Characteristically, these features exhibit distinct sublattice localization within the three-site basis of the kagome lattice. However, experimental proof of this sublattice character is challenging and requires direct access to both the real-space wave function and its associated momentum-space texture. Here, we implement an acoustic kagome lattice on the cm scale and measure the full excitation spectrum, thereby imaging the wave function at each lattice site, including both amplitude and phase. This enables investigation of the momentum-dependent sublattice texture across the complete band structure, particularly at the flat band and at the mixed- and pure-sublattice van Hove singularities. Our results are in excellent agreement with minimal tight-binding model calculations and constitutes the first direct experimental observation of the sublattice-resolved band structure in a kagome lattice.