Charge-density wave fluctuation driven composite order in the layered Kagome Metals

Abstract

The newly 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. Besides superconductivity, these materials exhibit a charge-density wave (CDW) phase occurring at around 100 K, whose origin still remains elusive. The robust multi-component $2 \times 2$ CDW phase in these systems is of great interest due to the presence of an unusually large anomalous Hall effect. In quasi-2D systems with weak inter-layer coupling fluctuation driven exotic phases may appear. In particular in systems with multi-component 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 fluctuation-driven regime of composite CDW order may exist in thin films of kagome metals above the CDW transition temperature. We also find that the transition from the composite to individual CDW order is in the $\mathbb{Z}_3$ Potts universality class. Our findings suggest possible presence of exotic phases in the weakly coupled layered kagome metals, more so in the newly synthesized thin films of kagome metals.Comment: 7 pages, 3 figure