Robustness of the unidirectional stripe order in the kagome superconductor CsV3Sb5

V-based kagome materials AV(3)Sb(5) (A = K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a (0) x 2a (0) CDW (charge density wave with in-plane 2 x 2 superlattice modulation) in AV(3)Sb(5), an additional 1 x 4 (4a (0)) unidirectional stripe order has been observed at the Sb surface of RbV3Sb5 and CsV3Sb5. However, the stability and electronic nature of the 4a (0) stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a (0) stripe order on the Sb-terminated surface of CsV3Sb5. We find that the 4a (0) stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a (0) stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV3Sb5.