Exploring pairing symmetry in CsV₃Sb₅-derived Kagome superconductors by ultrahigh-resolution ARPES 

Yigui Zhong

The newly discovered kagome superconductors AV₃Sb₅ (A=K, Rb, Cs) provide a promising platform for investigating the interplay between band topology, electronic order, and lattice geometry [Nat. Phys. 18, 137 (2021), Nature 612, 647 (2022)]. Despite extensive research efforts on this system, the nature of the superconducting ground state remains elusive and a consensus on the electron pairing symmetry has not been achieved so far. During the long-term research of superconductors, angle-resolved photoemission spectroscopy (ARPES) has been proven to be a powerful tool to directly measure the superconducting gap in the momentum space. In this talk, I will report our ultrahigh resolution and low-temperature ARPES studies on two exemplary CsV₃Sb₅-derived kagome superconductors — Cs(V0.93Nb0.07)₃Sb₅ with the appearance of charge order and Cs(V0.86Ta0.14)₃Sb₅ without charge order in the normal state [Nature 617, 488 (2023)]. Our new updated results of the superconducting gap on pristine CsV₃Sb₅ will be also presented in this talk. Additionally, I will present our studies of electronic kinks in the band structure [Nat. Commun. 14, 1945 (2023)] and temperature-dependent muon spin relaxation rate. Finally, the possible pairing mechanisms for these kagome superconductors based on these results will be discussed.