Journal Article

Chiral kagome superconductivity modulations with residual Fermi arcs

Dürrnagel, Matteo, Holbæk, Sofie Castro, Yao, Yugui, Zhao, Yuanyuan, Chang, Guoqing, Song, Wei, Yin, Jia-Xin, Qin, Hailang, Fu, Ruiqing, Shi, Youguo, Wang, Qianghua, Liu, Guowei, Xu, Gang, Zhang, Zhongyi, Wu, Xianxin, Deng, Hanbin, Liu, Jinjin, Hohmann, Hendrik, Guguchia, Zurab, Neupert, Titus, Liu, Hongxiong, Zhou, Sen, Yan, Xiao-Yu, Fischer, Mark H., Wang, Zhiwei, Thomale, Ronny, Yang, Tianyu, Yi, Mingsheng, Xu, Xitong

2024

Overview

Superconductivity involving finite-momentum pairing 1 can lead to spatial-gap and pair-density modulations, as well as Bogoliubov Fermi states within the superconducting gap. However, the experimental realization of their intertwined relations has been challenging. Here we detect chiral kagome superconductivity modulations with residual Fermi arcs in KV 3 Sb 5 and CsV 3 Sb 5 using normal and Josephson scanning tunnelling microscopy down to 30 millikelvin with a resolved electronic energy difference at the microelectronvolt level. We observe a U-shaped superconducting gap with flat residual in-gap states. This gap shows chiral 2 a  × 2 a spatial modulations with magnetic-field-tunable chirality, which align with the chiral 2 a ×  2 a pair-density modulations observed through Josephson tunnelling. These findings demonstrate a chiral pair density wave (PDW) that breaks time-reversal symmetry. Quasiparticle interference imaging of the in-gap zero-energy states reveals segmented arcs, with high-temperature data linking them to parts of the reconstructed vanadium d -orbital states within the charge order. The detected residual Fermi arcs can be explained by the partial suppression of these d -orbital states through an interorbital 2 a ×  2 a PDW and thus serve as candidate Bogoliubov Fermi states. In addition, we differentiate the observed PDW order from impurity-induced gap modulations. Our observations not only uncover a chiral PDW order with orbital selectivity but also show the fundamental space–momentum correspondence inherent in finite-momentum-paired superconductivity. Using normal and Josephson scanning tunnelling microscopy, chiral kagome superconductivity modulations with corresponding residual Fermi arcs are detected in KV 3 Sb 5 and CsV 3 Sb 5 .

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/301/119/1003 / 639/766/119/1003 / 639/766/119/995 / Bias / Chirality / Density / Electrons / Elementary excitations / Energy / Fourier transforms / High temperature / Humanities and Social Sciences / Magnetic fields / Microscopy / Momentum / multidisciplinary / Scanning tunneling microscopy / Science / Science (multidisciplinary) / Superconductivity / Symmetry / Temperature data / Topography / Vanadium