Angle-resolved photoemission spectroscopy study on kagome superconductor AV₃Sb₅ (A = K, Rb, Cs)

The recently discovered kagome superconductors AV₃Sb₅ (A= K, Rb, Cs) provide a new platform to explore intertwined symmetry-breaking orders. However, great controversies exist to date, including the origin of charge density wave (CDW), the unconventional or conventional nature of superconductivity, and the presence or absence of time-reversal symmetry breaking. A thorough understanding of the fundamental electronic structure is crucial for addressing these disputes. In this review, we provide an extensive summary of the key structural and electronic properties of AV₃Sb₅ compounds and evaluate the current research on their unconventional electronic order, especially the superconductivity and CDW, with a particular focus on insights from angle-resolved photoemission spectroscopy studies. We expect this review to be timely due to the convergence of various experimentally observed phenomena related to the CDW and superconducting order parameters in AV₃Sb₅ compounds. Our goal is to guide future investigations aimed at uncovering the microscopic origins of these unconventional electronic properties in kagome superconductors.