Magnetic Penetration Depth Measurements of Kagome Superconductors AV₃Sb₅ (A=Cs, K, Rb)

The recently discovered kagome metal series AV₃Sb₅ (A=Cs, K, Rb) hosts a variety of electronic states, including superconductivity. Key questions about the superconducting phase are what is the structure of the superconducting gap and what is the pairing symmetry. Some features of the superconducting gap, such as the presence of nodes, can be inferred from the temperature dependence of the magnetic penetration depth. The penetration depth in CsV₃Sb₅ has been determined via several probes ^{[1],[2],[3],[4]}, but similar measurements on KV₃Sb₅ and RbV₃Sb₅ are limited ^[5],[6], and a careful comparison between the three compounds is lacking. In this work, we use scanning superconducting quantum interference device (SQUID) susceptometry to measure, side by side, the temperature dependence of the magnetic penetration depth of the series of kagome superconductors AV₃Sb₅ (A=Cs, K, Rb). We will discuss what we can infer about the superconducting gap from these measurements.



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