Browsing by Author "Sales, Brian C."

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    Imaging real-space flat band localization in kagome magnet FeSn
    (Springer Nature, 2023) Multer, Daniel; Yin, Jia-Xin; Hossain, Md Shafayat; Yang, Xian; Sales, Brian C.; Miao, Hu; Meier, William R.; Jiang, Yu-Xiao; Xie, Yaofeng; Dai, Pengcheng; Liu, Jianpeng; Deng, Hanbin; Lei, Hechang; Lian, Biao; Zahid Hasan, M.; Rice Center for Quantum Materials
    Kagome lattices host flat bands due to their frustrated lattice geometry, which leads to destructive quantum interference of electron wave functions. Here, we report imaging of the kagome flat band localization in real-space using scanning tunneling microscopy. We identify both the Fe3Sn kagome lattice layer and the Sn2 honeycomb layer with atomic resolution in kagome antiferromagnet FeSn. On the Fe3Sn lattice, at the flat band energy determined by the angle resolved photoemission spectroscopy, tunneling spectroscopy detects an unusual state localized uniquely at the Fe kagome lattice network. We further show that the vectorial in-plane magnetic field manipulates the spatial anisotropy of the localization state within each kagome unit cell. Our results are consistent with the real-space flat band localization in the magnetic kagome lattice. We further discuss the magnetic tuning of flat band localization under the spin–orbit coupled magnetic kagome lattice model.
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    Surface terminations and layer-resolved tunneling spectroscopy of the 122 iron pnictide superconductors
    (American Physical Society, 2019) Li, Ang; Yin, Jia-Xin; Wang, Jihui; Wu, Zheng; Ma, Jihua; Sefat, Athena S.; Sales, Brian C.; Mandrus, David G.; McGuire, Michael A.; Jin, Rongying; Zhang, Chenglin; Dai, Pengcheng; Lv, Bing; Chu, Ching-Wu; Liang, Xuejin; Hor, P.-H.; Ting, C.-S.; Pan, Shuheng H.
    The surface terminations of 122-type alkaline earth metal iron pnictides AEFe2As2(AE=Ca,Ba) are investigated with scanning tunneling microscopy/spectroscopy. Cleaving these crystals at a cryogenic temperature yields a large majority of terminations with an atomically resolved (√2 × √2)R45 or 1 × 2 lattice, as well as a very rare termination of 1 × 1 lattice symmetry. By analyzing the lattice registration and selective chemical marking, we identify these terminations as (√2 × √2)R45-reconstructed AE, 1 × 2-reconstructed As, and (√2 × √2)R45-reconstructed Fe surface layers, respectively. Layer-resolved tunneling spectroscopy on these terminating surfaces reveals a well-defined superconducting energy gap on the As terminations, while the gap features become weaker on the AE terminations and absent on the Fe terminations. The superconducting gap is hardly affected locally by the As or AE surface reconstructions. The definitive identification of the surface terminations and the associated spectroscopic signatures shed light on the essential roles of As and the pnictogen-iron-pnictogen trilayer building block in iron-based superconductivity.