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

Ever since the discovery of the charge density wave (CDW) transition in the kagome metal CsV3Sb5, 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 (mE2g). 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 CsV3Sb5 using three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficient mE2g 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 mA1g 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 A1g channel.