Evidence of a strongly anisotropic superconducting gap in kagome superconductor CsV₃Sb₅: A study of directional point-contact Andreev reflection spectroscopy

In the recently discovered V-based kagome superconductors AV₃Sb₅ (A = K, Rb, Cs), superconductivity intertwines with an unconventional charge density wave (CDW), raising fundamental questions concerning the superconducting gap structure in the presence of such intertwined orders. Here, we perform the first directional point-contact Andreev reflection (PCAR) spectroscopy measurement on CsV₃Sb₅ to probe its superconducting gap structure. Strikingly distinct PCAR spectra emerge depending on the current injection direction: an in-gap zero-bias conductance peak dominates for currents parallel to the ab-plane, contrasting to a gap-like structure observed perpendicularly. Quantitative analysis using a modified BTK-model estimates a pronounced gap anisotropy of ∼ 70% with a gap minimum ∼ 0.15 meV. These results provide a foundation for further understanding the nature of the topological superconducting state on the sample edges.