Real-space imaging of kagome flat band localization in Fe₃Sn₂

In geometrically frustrated lattices, flat bands can arise from destructive quantum interference, providing an ideal platform for exploring strong electron correlations. However, direct real-space evidence of their predicted atomic-scale electron localization remains elusive. By employing scanning tunneling microscopy/spectroscopy, with a focus on quasiparticle interference imaging, we demonstrate unambiguous atomic-scale localization of flat band electrons in the kagome metal Fe₃Sn₂. Crucially, quasiparticle interference imaging reveals a complete suppression of scattering wavevectors and standing waves exclusively at the flat band energy, indicating the absence of long-range coherent propagation. This disappearance of the quasiparticle interference signal, attributable to the non-propagating wavefunctions inherent to the kagome flat band, directly confirms real-space electron localization. These findings resolve the microscopic link between quantum interference and localization of flat band electrons, paving the way for engineering correlated quantum states.