Electron-Correlation-Induced Charge Density Waves and Magnetism-Related Energy Gap in Kagome FeGe Unraveled by STM/STS.

As the first magnetic Kagome material exhibiting charge density waves (CDWs), FeGe has garnered widespread research interest. In this work, we utilized low-temperature, high-magnetic-field scanning tunneling microscopy/spectroscopy to investigate both the CDWs and magnetism in FeGe. We observed coexisting short-range 2 × 2 and √3 × √3 CDW patterns, which are spatially exclusive with Ge1 site defects in the Kagome layer, suggesting that CDW formation is related to Ge1-dimerization involving electron correlations. Using a spin-polarized tip, we identified the A-type antiferromagnetic (AFM) structure, which undergoes a gradual spin-flop transition with increasing magnetic field. The gap opened at the Fermi energy evolves with the magnetic structure transition but remains insensitive to the presence of CDWs. These results underscore the role of electron correlations in the formation of the CDWs in FeGe and identify the magnetism origin of the low-energy gap, revealing a compatibility between AFM order and CDWs in FeGe.