Polarity-dependent charge density wave in the kagome superconductor CsV3Sb5

Polar surface and interface play pivotal roles for realizing exotic properties of materials, and search for such polar states is of crucial importance for expanding materials' functionality. Here we report microfocused angle-resolved photoemission spectroscopy of CsV3Sb5, a member of recently discovered kagome superconductors AV3Sb5 (A = K, Rb, and Cs) and show evidence for the polar nature of the cleaved surface which is characterized by Cs- and Sb-terminated surfaces with markedly different fermiology. The Cs-terminated surface shows intriguing doubling of V-derived bands at low temperatures associated with the band folding due to the three-dimensional charge density wave (CDW), whereas the Sb-terminated one shows no band doubling or resultant CDW-gap opening indicative of the suppression of bulk-originated CDW due to polar charge. Such polar-surface-dependent band structures must be incorporated for understanding the origin of unconventional superconducting and charge order at the surface of AV3Sb5.