Evolution of magnetic excitations in FeSe1-xSx across the nematic critical point

The evolution of magnetism, nematic order and superconductivity in the multi-degree-of-freedom system is one of the theme issues in the study of iron-based superconductors. As the structurally simplest system, FeSe has distinct phase relations with iron pnictides under hydrostatic pressure and has raised significant interests. Isovalent S substitution introduces "chemical pressure", expands the band widths and reduces the electronic correlations. It completely suppresses the nematic order of FeSe at around 17% S doping level and tunes the superconducting pairing states. Thus it offers a good platform to study the interplay between electronic correlation, magnetism, nematicity and superconductivity. Here we propose to investigate the evolution of the magnetic excitation across the nematic critical point, via inelastic neutron scattering on FeSe0.9S0.1 and FeSe0.8S0.2