Nematic quantum criticality in FeSe$_{1-}_{x}$S$_{x}$ revealed by elastoresistance measurements

Electronic nematicity and its connection to the high-temperature superconductivity is one of the central issues in iron-based superconductors. Among them, FeSe is unique in that it exhibits a tetragonal-to-orthorhombic structural transition but no antiferromagnetic order, which enables us to study the nematicity without the effect of magnetism. Here we report on elastoresistance measurements in FeSe$_{1-}_{x}$S$_{x}$ evidencing a nonmagnetic nematic quantum critical point near $x\sim $ 0.2. When the Se site is substituted by the isovalent S, the structural transition temperature is reduced gradually and it vanishes above $x\sim $ 0.2. From the changes in in-plane resistivity induced by anisotropic strain, we evaluate the nematic susceptibility which shows Curie-Weiss-like temperature dependence. We find that with increasing $x$ the Weiss temperature changes its sign indicating a quantum critical point, while there is no sign of antiferromagnetism for all samples. The superconducting transition temperature does not show a significant change with S concentration, suggesting that the nonmagnetic nematic quantum criticality does not help to enhance superconductivity in this system.