In the recently discovered kagome superconductor AV3Sb5 (A = K, Rb, and Cs), superconductivity is intertwined with an unconventional charge density wave order. The pairing symmetry remains elusive owing to the lack of direct measurement of the superconducting gap in the momentum space. Here, utilizing laser-based ultra-high-resolution and low-temperature angle-resolved photoemission spectroscopy, we observe Fermi-surface-dependent anisotropic Cooper pairing in kagome superconductor CsV3Sb5. We detect a highly anisotropic superconducting gap structure with anisotropy exceeding 80% and a gap maximum along the V-V bond direction on a Fermi surface originating from the 3d-orbital electrons of the V kagome lattice. This is in stark contrast to the isotropic superconducting gap structure on the Fermi surface occupied by Sb 5p-orbital electrons. Our direct observation of the Fermi-surface-dependent anisotropic pairing in CsV3Sb5 is fundamental for understanding the intertwined orders in the ground state of kagome superconductors.
@article{arxiv.2404.18472,
title = {Observation of Fermi-surface-dependent anisotropic Cooper pairing in kagome superconductor CsV3Sb5},
author = {Akifumi Mine and Yigui Zhong and Jinjin Liu and Takeshi Suzuki and Sahand Najafzadeh and Takumi Uchiyama and Jia-Xin Yin and Xianxin Wu and Xun Shi and Zhiwei Wang and Yugui Yao and Kozo Okazaki},
journal= {arXiv preprint arXiv:2404.18472},
year = {2025}
}