The recently discovered kagome metal series AV3Sb5 (A=K, Rb, Cs) exhibits topologically nontrivial band structures, chiral charge order and superconductivity, presenting a unique platform for realizing exotic electronic states. The nature of the superconducting state and the corresponding pairing symmetry are key questions that demand experimental clarification. Here, using a technique based on the tunneling diode oscillator, the magnetic penetration depth Δλ(T) of CsV3Sb5 was measured down to 0.07 K. A clear exponential behavior in Δλ(T) with marked deviations from a T or T2 temperature dependence is observed at low temperatures, indicating a deficiency of nodal quasiparticles. Temperature dependence of the superfluid density and electronic specific heat can be described by two-gap s-wave superconductivity, consistent with the presence of multiple Fermi surfaces in CsV3Sb5. These results evidence nodeless superconductivity in CsV3Sb5 under ambient pressure, and constrain the allowed pairing symmetry.
@article{arxiv.2103.11796,
title = {Nodeless superconductivity in the kagome metal CsV$_3$Sb$_5$},
author = {Weiyin Duan and Zhiyong Nie and Shuaishuai Luo and Fanghang Yu and Brenden R. Ortiz and Lichang Yin and Hang Su and Feng Du and An Wang and Ye Chen and Xin Lu and Jianjun Ying and Stephen D. Wilson and Xianhui Chen and Yu Song and Huiqiu Yuan},
journal= {arXiv preprint arXiv:2103.11796},
year = {2021}
}