Polarity-dependent charge-density wave in a kagome superconductor CsV3Sb5

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal how polar surface termination influences charge-density wave behavior in the kagome superconductor CsV3Sb5, highlighting surface-dependent electronic properties.

Contribution

It demonstrates the polar nature of the cleaved surface in CsV3Sb5 and its impact on charge-density wave phenomena, providing new insights into surface effects in kagome superconductors.

Findings

Cs-terminated surface exhibits band doubling and CDW-related band folding.

Sb-terminated surface shows no band doubling or CDW gap.

Polar surface termination affects the electronic structure and charge order.

Abstract

Polar surface and interface play a pivotal role for realizing exotic properties of materials, and a search for such polar states is of crucial importance for expanding materials' functionality. Here we report micro-focused angle-resolved photoemission spectroscopy of CsV3Sb5, a member of recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs), and show evidence for the polar nature of 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 temperature 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 structure must be incorporated for understanding the origin of unconventional superconducting and charge order at the surface of AV3Sb5.