Kagome superconductors AV₃Sb₅ (A = K, Rb, Cs)

The quasi-two-dimensional kagome materials AV₃Sb₅ (A = K, Rb, Cs) were found to be a prime example of kagome superconductors, a new quantum platform to investigate the interplay between electron correlation effects, topology and geometric frustration. In this review, we report recent progress on the experimental and theoretical studies of AV₃Sb₅ and provide a broad picture of this fast-developing field in order to stimulate an expanded search for unconventional kagome superconductors. We review the electronic properties of AV₃Sb₅, the experimental measurements of the charge density wave state, evidence of time-reversal symmetry breaking and other potential hidden symmetry breaking in these materials. A variety of theoretical proposals and models that address the nature of the time-reversal symmetry breaking are discussed. Finally, we review the superconducting properties of AV₃Sb₅, especially the potential pairing symmetries and the interplay between superconductivity and the charge density wave state.