近日，南方科技大学的殷嘉鑫与中国科学院物理研究所的石友国以及北京理工大学的王立志等人合作并取得一项新进展。经过不懈努力，他们揭示残余费米弧的手性笼目超导调制。相关研究成果已于2024年8月21日在国际权威学术期刊《自然》上发表。

该研究团队使用常规和约瑟夫森扫描隧道显微镜，在30毫开尔文的温度下，以微电子伏特级别的电子能量差分辨率，在KV₃Sb₅和CsV₃Sb₅中检测到了具有剩余费米弧的手性笼目超导性调制。研究人员观察到了一个U形的超导间隙，其间隙内具有平坦的剩余态。该间隙显示出具有磁场可调手性的2a × 2a空间调制，这与通过约瑟夫森隧穿观察到的2a × 2a手性配对密度调制相一致。这些发现表明了一种打破时间反演对称性的手性配对密度波（PDW）。

间隙内零能量态的准粒子干涉成像揭示了分段弧，高温数据将其与电荷序中重建的钒d轨道态的部分联系起来。检测到的剩余费米弧可通过轨道间2a × 2a PDW对这些d轨道态的部分抑制来解释，因此可作为玻戈留波夫费米态的候选。此外，研究人员将观察到的PDW序与杂质诱导的间隙调制区分开来。这项观察结果不仅揭示了具有轨道选择性的手性PDW序，还展示了有限动量配对超导性中固有的基本空间-动量对应关系。

据悉，涉及有限动量配对的超导性可导致空间间隙和配对密度调制，以及超导间隙内的玻戈留波夫费米态。然而，在实验上实现它们之间错综复杂的关系一直是个挑战。

附：英文原文

Title: Chiral kagome superconductivity modulations with residual Fermi arcs

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

Issue&Volume: 2024-08-21

Abstract: Superconductivity involving finite-momentum pairing 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 KV₃Sb₅ and CsV₃Sb₅ using normal and Josephson scanning tunnelling microscopy down to 30millikelvin 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 2a × 2a spatial modulations with magnetic-field-tunable chirality, which align with the chiral 2a × 2a 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 2a × 2a 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.

DOI: 10.1038/s41586-024-07798-y

Source: https://www.nature.com/articles/s41586-024-07798-y