Quantum oscillation study of the kagome superconductor

Kagome metals AV₃Sb₅ (A = K, Rb, Cs) are recently discovered platforms featuring an unusual charge-density-wave (CDW) order and superconductivity. The electronic band structure of a kagome lattice can host both flat bands as well as Dirac-like bands, offering the possibility to stabilize various quantum states. I will present the electronic structure study of CsV₃Sb₅ via Shubnikov-de Haas quantum oscillations. We unambiguously reveal the existence of new frequencies with large frequencies ranging from ∼2085 T to ∼2717 T in thin flakes when the magnetic field is along the c-axis. These quasi-two-dimensional frequencies correspond to ∼52% to 67% of the CDW-distorted Brillouin zone volume. The Lifshitz-Kosevich analysis further uncovers surprisingly small cyclotron effective masses, of the order of ∼0.1 me, for these frequencies. Consequently, a large number of high-velocity carriers exists in the thin flake of CsV₃Sb₅. Furthermore, the detected high frequencies cannot be captured by the DFT calculations even with the CDW distortion considered. Our results provide new information for understanding the fermiology of the kagome superconductor AV₃Sb₅.