@article{51a1762adb7440c8aa7639966b7ade9d,
title = "Fermion–boson many-body interplay in a frustrated kagome paramagnet",
abstract = "Kagome-nets, appearing in electronic, photonic and cold-atom systems, host frustrated fermionic and bosonic excitations. However, it is rare to find a system to study their fermion–boson many-body interplay. Here we use state-of-the-art scanning tunneling microscopy/spectroscopy to discover unusual electronic coupling to flat-band phonons in a layered kagome paramagnet, CoSn. We image the kagome structure with unprecedented atomic resolution and observe the striking bosonic mode interacting with dispersive kagome electrons near the Fermi surface. At this mode energy, the fermionic quasi-particle dispersion exhibits a pronounced renormalization, signaling a giant coupling to bosons. Through the self-energy analysis, first-principles calculation, and a lattice vibration model, we present evidence that this mode arises from the geometrically frustrated phonon flat-band, which is the lattice bosonic analog of the kagome electron flat-band. Our findings provide the first example of kagome bosonic mode (flat-band phonon) in electronic excitations and its strong interaction with fermionic degrees of freedom in kagome-net materials.",
author = "Yin, {J. X.} and Nana Shumiya and Sougata Mardanya and Qi Wang and Zhang, {Songtian S.} and Tien, {Hung Ju} and Daniel Multer and Yuxiao Jiang and Guangming Cheng and Nan Yao and Shangfei Wu and Desheng Wu and Liangzi Deng and Zhipeng Ye and Rui He and Guoqing Chang and Zhonghao Liu and Kun Jiang and Ziqiang Wang and Titus Neupert and Amit Agarwal and Chang, {Tay Rong} and Chu, {Ching Wu} and Hechang Lei and Hasan, {M. Zahid}",
note = "Funding Information: We acknowledge insightful discussions with Biao Lian and Zhida Song, and technical assistance from Limin Liu and Gaihua Ye. Experimental and theoretical work at Princeton University was supported by the Gordon and Betty Moore Foundation (Grant No. GBMF4547 and GBMF9461/Hasan). Sample characterization was supported by the United States Department of Energy (US DOE) under the Basic Energy Sciences programme (Grant No. DOE/BES DE-FG-02-05ER46200). M.Z.H. acknowledges support from Lawrence Berkeley National Laboratory and the Miller Institute of Basic Research in Science at the University of California, Berkeley in the form of a Visiting Miller Professorship. This work benefited from partial lab infra-structure support under NSF-DMR-1507585. M.Z.H. also acknowledges visiting scientist support from IQIMat the California Institute of Technology. The work at Renmin University was supported by the National Key R&D Program of China (Grants Nos. 2016YFA0300504 and 2018YFE0202600), the National Natural Science Foundation of China (No. 11774423,11822412), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (RUC) (18XNLG14, 19XNLG17). The authors acknowledge the use of Princeton{\textquoteright}s Imaging and Analysis Center, which is partially supported by the Princeton Center for Complex Materials, a National Science Foundation (NSF)-MRSEC program (DMR-1420541). T.-R.C. was supported from the Young Scholar Fellowship Program by the Ministry of Science and Technology (MOST) in Taiwan, under MOST Grant for the Columbus Program No. MOST109-2636-M-006-002, National Cheng Kung University, Taiwan, and National Center for Theoretical Sciences (NCTS), Taiwan. This work was supported partially by the MOST, Taiwan, grant MOST107-2627-E-006-001. This research was supported in part by Higher Education Sprout Project, Ministry of Education to the Headquarters of University. Z.W. and K.J. acknowledge US DOE Grant No. DE-FG02-99ER45747. T.N. acknowledges support from the European Union{\textquoteright}s Horizon 2020 research and innovation programme (ERC-StG-Neupert-757867-PARATOP). The work performed at the Texas Center for Superconductivity at the University of Houston is supported by the U.S. Air Force Office of Scientific Research Grant FA9550-15-1-0236, the T.L.L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through the Texas Center for Superconductivity at the University of Houston. R.H. acknowledges support by NSF CAREER Grant No. DMR-1760668 and NSF MRI Grant No. DMR-1337207. Publisher Copyright: {\textcopyright} 2020, The Author(s).",
year = "2020",
month = dec,
day = "1",
doi = "10.1038/s41467-020-17464-2",
language = "English (US)",
volume = "11",
journal = "Nature Communications",
issn = "2041-1723",
publisher = "Nature Publishing Group",
number = "1",
}