Browsing by Author "Liu, Zhaoyu"

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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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    Nematic Quantum Critical Fluctuations in BaFe2−xNixAs2
    (American Physical Society, 2016) Liu, Zhaoyu; Gu, Yanhong; Zhang, Wei; Gong, Dongliang; Zhang, Wenliang; Xie, Tao; Lu, Xingye; Ma, Xiaoyan; Zhang, Xiaotian; Zhang, Rui; Zhu, Jun; Ren, Cong; Shan, Lei; Qiu, Xianggang; Dai, Pengcheng; Yang, Yi-feng; Luo, Huiqian; Li, Shiliang
    We have systematically studied the nematic fluctuations in the electron-doped iron-based superconductor BaFe2−xNixAs2 by measuring the in-plane resistance change under uniaxial pressure. While the nematic quantum critical point can be identified through the measurements along the (110) direction, as studied previously, quantum and thermal critical fluctuations cannot be distinguished due to similar Curie-Weiss-like behaviors. Here we find that a sizable pressure-dependent resistivity along the (100) direction is present in all doping levels, which is against the simple picture of an Ising-type nematic model. The signal along the (100) direction becomes maximum at optimal doping, suggesting that it is associated with nematic quantum critical fluctuations. Our results indicate that thermal fluctuations from striped antiferromagnetic order dominate the underdoped regime along the (110) direction. We argue that either there is a strong coupling between the quantum critical fluctuations and the fermions, or more exotically, a higher symmetry may be present around optimal doping.