Disordered charge density waves in the kagome metal FeGe

The discovery of a charge density wave (CDW) in the antiferromagnetic kagome metal FeGe has prompted interest in the interplay between kagome physics, CDW, and magnetism. However, a crucial aspect for understanding these emergent phenomena-the precise CDW structure-remains ambiguous. Recent studies have assumed uniformly distributed Ge dimers, but this assumption is problematic. The predicted band structure based on this model exhibits an abrupt disappearance of a Ge-$p$ band in the Fermi surface, contradicting experimental observations from angle-resolved photoemission spectroscopy (ARPES). In this study, we propose that a CDW phase with disordered Ge dimers can reconcile theoretical predictions with ARPES results. This model reproduces the observed CDW gaps while preserving the Ge-$p$ band. Depending on experimental conditions, Ge dimers can be randomly distributed or exhibit phase separation from pristine regions. Our findings reveal the crucial role of Ge dimer disorder in the FeGe CDW and suggest potential implications of this disorder for other properties, such as magnetism and transport, in this system.