Microscopic evidence for anisotropic multigap superconductivity in the CsV3Sb5 kagome superconductor

The recently discovered kagome superconductor CsV$_3$Sb$_5$ ($T_c \simeq 2.5$ K) has been found to host charge order as well a non-trivial band topology, encompassing multiple Dirac points and probable surface states. Such complex phenomenologically rich system is, therefore, an ideal playground for observing unusual electronic phases. Here, we report on microscopic studies of its anisotropic superconducting properties by means transverse-field muon spin rotation ($\mu$SR) experiments. temperature dependences the in-plane out-of-plane components magnetic penetration depth $\lambda_{ab}^{-2}(T)$ $\lambda_{c}^{-2}(T)$ indicate that parameter exhibits two-gap ($s+s$)-wave symmetry, reflecting Fermi surfaces CsV3Sb5. multiband nature superconductivity is further validated different $\gamma_\lambda(T)$ upper critical field $\gamma_{\rm B_{c2}}(T)$, both in close analogy with known MgB$_2$. Remarkably, high value $T_c/\lambda^{-2}(0)$ ratio orientations strongly suggests unconventional superconductivity. relaxation rates obtained from zero $\mu$SR experiments do not show noticeable change across transition, indicating does break time reversal symmetry.