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1. Absence of E2g Nematic Instability and Dominant A1g Response in the Kagome Metal CsV3Sb5

   https://doi.org/10.1103/PhysRevX.14.031015  

   Liu, Zhaoyu ; Shi, Yue ; Jiang, Qianni ; Rosenberg, Elliott W ; DeStefano, Jonathan M ; Liu, Jinjin ; Hu, Chaowei ; Zhao, Yuzhou ; Wang, Zhiwei ; Yao, Yugui ; et al ( July 2024 , Physical Review X)

   Ever since the discovery of the charge density wave (CDW) transition in the kagome metal${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, 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 ($T_{\mathrm{CDW}}$), an additional electronic nematic instability well below$T_{\mathrm{CDW}}$has been reported based on the diverging elastoresistivity coefficient in the anisotropic channel ($m_{E_{2g}}$). Verifying the existence of a nematic transition below$T_{\mathrm{CDW}}$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${\mathrm{CsV}}_3{\mathrm{Sb}}_5$using three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficient$m_{E_{2g}}$is temperature independent, except for a step jump at$T_{\mathrm{CDW}}$. 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$m_{A_{1g}}$increases below$T_{\mathrm{CDW}}$, reaching a peak value of 90 at$T^{*}=20\mathrm{K}$. 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$A_{1g}$channel.