Browsing by Author "Yin, Jia-Xin"

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    Conventional superconductivity in the doped kagome superconductor Cs(V0.86Ta0.14)3Sb5 from vortex lattice studies
    (Springer Nature, 2024) Xie, Yaofeng; Chalus, Nathan; Wang, Zhiwei; Yao, Weiliang; Liu, Jinjin; Yao, Yugui; White, Jonathan S.; DeBeer-Schmitt, Lisa M.; Yin, Jia-Xin; Dai, Pengcheng; Eskildsen, Morten Ring
    A hallmark of unconventional superconductors is a complex electronic phase diagram where intertwined orders of charge-spin-lattice degrees of freedom compete and coexist. While the kagome metals such as CsV3Sb5 also exhibit complex behavior, involving coexisting charge density wave order and superconductivity, much is unclear about the microscopic origin of the superconducting pairing. We study the vortex lattice in the superconducting state of Cs(V0.86Ta0.14)3Sb5, where the Ta-doping suppresses charge order and enhances superconductivity. Using small-angle neutron scattering, a strictly bulk probe, we show that the vortex lattice exhibits a strikingly conventional behavior. This includes a triangular symmetry with a period consistent with 2e-pairing, a field dependent scattering intensity that follows a London model, and a temperature dependence consistent with a uniform superconducting gap. Our results suggest that optimal bulk superconductivity in Cs(V1−xTax)3Sb5 arises from a conventional Bardeen-Cooper-Schrieffer electron-lattice coupling, different from spin fluctuation mediated unconventional copper- and iron-based superconductors.
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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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    Observation of flat bands and Dirac cones in a pyrochlore lattice superconductor
    (Springer Nature, 2024) Huang, Jianwei; Setty, Chandan; Deng, Liangzi; You, Jing-Yang; Liu, Hongxiong; Shao, Sen; Oh, Ji Seop; Guo, Yucheng; Zhang, Yichen; Yue, Ziqin; Yin, Jia-Xin; Hashimoto, Makoto; Lu, Donghui; Gorovikov, Sergey; Dai, Pengcheng; Denlinger, Jonathan D.; Allen, J. W.; Hasan, M. Zahid; Feng, Yuan-Ping; Birgeneau, Robert J.; Shi, Youguo; Chu, Ching-Wu; Chang, Guoqing; Si, Qimiao; Yi, Ming; Rice Center for Quantum Materials
    Emergent phases often appear when the electronic kinetic energy is comparable to the Coulomb interactions. One approach to seek material systems as hosts of such emergent phases is to realize localization of electronic wavefunctions due to the geometric frustration inherent in the crystal structure, resulting in flat electronic bands. Recently, such efforts have found a wide range of exotic phases in the two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge order, nematicity, and superconductivity. However, the interlayer coupling of the kagome layers disrupts the destructive interference needed to completely quench the kinetic energy. Here we demonstrate that an interwoven kagome network—a pyrochlore lattice—can host a three dimensional (3D) localization of electron wavefunctions. Meanwhile, the nonsymmorphic symmetry of the pyrochlore lattice guarantees all band crossings at the Brillouin zone X point to be 3D gapless Dirac points, which was predicted theoretically but never yet observed experimentally. Through a combination of angle-resolved photoemission spectroscopy, fundamental lattice model and density functional theory calculations, we investigate the novel electronic structure of a Laves phase superconductor with a pyrochlore sublattice, CeRu2. We observe evidence of flat bands originating from the Ce 4f orbitals as well as flat bands from the 3D destructive interference of the Ru 4d orbitals. We further observe the nonsymmorphic symmetry-protected 3D gapless Dirac cone at the X point. Our work establishes the pyrochlore structure as a promising lattice platform to realize and tune novel emergent phases intertwining topology and many-body interactions.
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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.
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    The Magnetic Genome of Two-Dimensional van der Waals Materials
    (American Chemical Society, 2022) Wang, Qing Hua; Bedoya-Pinto, Amilcar; Blei, Mark; Dismukes, Avalon H.; Hamo, Assaf; Jenkins, Sarah; Koperski, Maciej; Liu, Yu; Sun, Qi-Chao; Telford, Evan J.; Kim, Hyun Ho; Augustin, Mathias; Vool, Uri; Yin, Jia-Xin; Li, Lu Hua; Falin, Alexey; Dean, Cory R.; Casanova, Fèlix; Evans, Richard F.L.; Chshiev, Mairbek; Mishchenko, Artem; Petrovic, Cedomir; He, Rui; Zhao, Liuyan; Tsen, Adam W.; Gerardot, Brian D.; Brotons-Gisbert, Mauro; Guguchia, Zurab; Roy, Xavier; Tongay, Sefaattin; Wang, Ziwei; Hasan, M. Zahid; Wrachtrup, Joerg; Yacoby, Amir; Fert, Albert; Parkin, Stuart; Novoselov, Kostya S.; Dai, Pengcheng; Balicas, Luis; Santos, Elton J.G.
    Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the brief time after their discovery, 2D magnets have blossomed into a rich area for investigation, where fundamental concepts in magnetism are challenged by the behavior of spins that can develop at the single layer limit. However, much effort is still needed in multiple fronts before 2D magnets can be routinely used for practical implementations. In this comprehensive review, prominent authors with expertise in complementary fields of 2D magnetism (i.e., synthesis, device engineering, magneto-optics, imaging, transport, mechanics, spin excitations, and theory and simulations) have joined together to provide a genome of current knowledge and a guideline for future developments in 2D magnetic materials research.