Robust short-range-ordered nematicity in FeSe evidenced by high-pressure NMR

We report high-pressure Se77 NMR studies on FeSe single crystals that reveal a prominent inhomogeneous NMR linewidth broadening upon cooling, with the magnetic field applied along the tetragonal [110] direction. The data indicate the existence of short-range-ordered, inhomogeneous electronic nematicity, which has surprisingly long time scales over milliseconds. The short-range order survives temperatures up to eight times the structural transition temperature, and remains robust against pressure, in contrast to the strong pressure-dependence of the orbital ordering, structural transition, and the ground state magnetism. Such an extended region of static nematicity in the (P,T) space of FeSe indicates an enormously large fluctuating regime, and provides fresh insights and constraints to the understanding of electronic nematicity in iron-based superconductors.