Browsing by Author "Yao, Yugui"

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    Absence of ${E}_{2g}$ Nematic Instability and Dominant ${A}_{1g}$ Response in the Kagome Metal ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$
    (American Physical Society, 2024) Liu, Zhaoyu; Shi, Yue; Jiang, Qianni; Rosenberg, Elliott W.; DeStefano, Jonathan M.; Liu, Jinjin; Hu, Chaowei; Zhao, Yuzhou; Wang, Zhiwei; Yao, Yugui; Graf, David; Dai, Pengcheng; Yang, Jihui; Xu, Xiaodong; Chu, Jiun-Haw
    Ever since the discovery of the charge density wave (CDW) transition in the kagome metal CsV3⁢Sb5, the nature of its symmetry breaking has been under intense debate. While evidence suggests that the rotational symmetry is already broken at the CDW transition temperature (𝑇CDW), an additional electronic nematic instability well below 𝑇CDW has been reported based on the diverging elastoresistivity coefficient in the anisotropic channel (𝑚𝐸2⁢𝑔). Verifying the existence of a nematic transition below 𝑇CDW is not only critical for establishing the correct description of the CDW order parameter, but also important for understanding low-temperature superconductivity. Here, we report elastoresistivity measurements of CsV3⁢Sb5 using three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficient 𝑚𝐸2⁢𝑔 is temperature independent, except for a step jump at 𝑇CDW. The absence of nematic fluctuations is further substantiated by measurements of the elastocaloric effect, which show no enhancement associated with nematic susceptibility. On the other hand, the symmetric elastoresistivity coefficient 𝑚𝐴1⁢𝑔 increases below 𝑇CDW, reaching a peak value of 90 at 𝑇*=20 K. Our results strongly indicate that the phase transition at 𝑇* is not nematic in nature and the previously reported diverging elastoresistivity is due to the contamination from the 𝐴1⁢𝑔 channel.
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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.