Charge density wave fluctuation driven composite order in layered kagome metals

The recently discovered kagome metals AV(3)Sb(5) (A = K, Rb, Cs) offer an exciting route to study exotic phases arising due to interplay between electronic correlations and topology. In addition to superconductivity, these materials exhibit a charge-density-wave (CDW) phase occurring at similar to 100 K, whose origin still remains elusive. The robust multicomponent 2 x 2 CDW phase in these systems is of great interest due to the presence of an unusually large anomalous Hall effect. In quasi-two-dimensional systems with weak interlayer coupling, fluctuation-driven exotic phases may appear. In systems with multicomponent order parameters, fluctuations may lead to establishment of composite order when only products of individual order parameters condense while the individual ones themselves remain disordered. We argue that such a fluctuation-driven regime of composite CDW order may exist in thin films of kagome metals above the CDW transition temperature. It is suggested that the melting of the trihexagonal state in the material doped away from the Van Hove singularities gives rise to a pseudogap regime where the spectral weight is concentrated in small pockets and most of the original Fermi surface is gapped. Our findings suggest the possible presence of exotic phases in the weakly coupled layered kagome metals, more so in the recently synthesized thin films of kagome metals.