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

Abstract

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.