Abstract
Coexisting density-wave and superconducting states along with the large anomalous Hall effect in the absence of local magnetism remain intriguing and enigmatic features of the AV3Sb5 kagome metals (A = K, Rb, Cs). Here, we demonstrate via optical spectroscopy and density-functional calculations that low-energy dynamics of KV3Sb5 is characterized by unconventional localized carriers, which are strongly renormalized across the density-wave transition and indicative of electronic correlations. Strong phonon anomalies are prominent not only below the density-wave transition, but also at high temperatures, suggesting an intricate interplay of phonons with the underlying electronic structure. We further propose the star-of-David and tri-hexagon (inverse star-of-David) configurations for the density-wave order in KV3Sb5. These configurations are strongly reminiscent of p-wave states expected in the Hubbard model on the kagome lattice at the filling level of the van Hove singularity. The proximity to this regime should have intriguing and far-reaching implications for the physics of KV3Sb5 and related materials.
Highlights
Kagome geometry of corner-sharing triangles plays a special role in condensed-matter physics
We argue that similarities between the proposed DW structures and the predicted phases of the kagome Hubbard model can be the key to understanding the peculiar physics of KV3Sb5
Our broadband optical spectroscopy experiments witness a strong renormalization of the DOS across TDW and set firm grounds for interpreting this anomaly as a charge-density-wave order
Summary
Kagome geometry of corner-sharing triangles plays a special role in condensed-matter physics In magnetic insulators, it may cause the highly entangled quantum spin liquid state with exotic fractionalized excitations[1]. It may cause the highly entangled quantum spin liquid state with exotic fractionalized excitations[1] Kagome metals exploit another aspect of this peculiar geometry, the simultaneous presence of linear and flat energy bands. The recent STM results on KV3Sb5 demonstrate chiral response under reversed magnetic field[17] and suggest that the low-temperature electronic state may not be a conventional charge order. This raises the question what this electronic state is, and in which form spin degrees of freedom can be embedded in it
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