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

Electronic nematicity, the spontaneous breaking of crystalline rotational symmetry, has been discovered in several strongly correlated electronic systems, including high Tc superconductors. Recently, several studies have suggested that the charge density wave in the kagome superconductor CsV₃Sb₅ breaks rotational symmetry—an intriguing possibility, as it would be a rare example of “three-state Potts nematicity,” in which there are three possible orientations in a hexagonal lattice. Here, we report that  CsV₃Sb₅ is probably not nematic, but it is very sensitive to isotropic strain. To reach this conclusion, we performed comprehensive elastoresistivity measurements using three different techniques. We also performed an elastocaloric measurement that measures the change of the sample temperature due to the applied strain. Our findings suggest that  CsV₃Sb₅ displays a weak, temperature-independent anisotropic response. It also shows a diverging response to the in-plane isotropic component of the strain. The previously reported diverging nematic susceptibility was probably due to contamination from this response. This new picture of the symmetry-breaking states in CsV₃Sb₅ provides clarity on past misconceptions and offers strong constraints on the symmetry of its charge density wave and the normal state of its superconductivity.