Fermi Surface Mapping and the Nature of Charge-Density-Wave Order in the Kagome Superconductor CsV3Sb5

The recently discovered family of AV(3)Sb(5) (A: K, Rb Cs) kagome metals possess a unique combination of nontrivial band topology, superconducting ground states, and signatures of electron correlations manifest via competing charge density wave order. Little is understood regarding the nature of the charge density wave (CDW) instability inherent to these compounds and the potential correlation with the onset of a large anomalous Hall response. To understand the impact of the CDWorder on the electronic structure in these systems, we present quantum oscillation measurements on single crystals of CsV(3)b(5). Our data provide direct evidence that the CDWinvokes a substantial reconstruction of the Fermi surface pockets associated with the vanadium orbitals and the kagome lattice framework. In conjunction with density functional theory modeling, we are able to identify split oscillation frequencies originating from reconstructed pockets built from vanadium orbitals and Dirac-like bands. Complementary diffraction measurements are further able to demonstrate that the CDW instability has a correlated phasing of distortions between neighboring V3Sb5 planes, and the average structure in the CDW state is proposed. These results provide critical insights into the underlying CDW instability in AV(3)Sb(5) kagome metals and support minimal models of CDW order arising from within the vanadium-based kagome lattice.