Direct Visualization of Distinct Charge Ordering Phases and Emergent Kondo Lattice Behavior in a van der Waals Ferromagnet

The intricate relationship between electronic and spin degrees of freedom in Kondo systems has drawn considerable attention, especially within d-electron systems, where the itinerant electrons mediate the charge and magnetic properties. Despite theoretical predictions, direct evidence of charge ordering phases within Kondo lattice systems has yet to be found. Here, we explore Fe₅GeTe₂, a two-dimensional (2D) ferromagnet, which offers a promising avenue to study these phenomena. Our scanning tunneling microscopy and spectroscopy (STM/STS) investigations reveal distinct charge density wave (CDW) behaviors in Fe₅GeTe₂. Notably, besides the √3 × √3 superstructure, which has been analyzed by various studies, we observe a distinct CDW with 2 × 2 modulation. Meanwhile, the Kondo lattice behavior coexists in the CDW phase; in the STS curve, a Fano-like peak emerges near the Fermi energy, indicating the Kondo interactions within this material. By comparing our experimental findings with theoretical studies on the charge and magnetic orderings, we propose a framework for understanding their mutual interplay. This work advances our understanding of Kondo physics in d-electron systems and highlights Fe₅GeTe₂ as a platform for future studies on 2D magnetism and potential spintronic applications.