Photoinduced dynamics of nematic order parameter in FeSe

Abstract

Nematicity is deemed a precursor of superconductivity in unconventional superconductors. Here, the authors investigate the formation of a nematic phase and the dynamics of nematic fluctuations in FeSe using ultrafast electron diffraction. They find an enhancement of the high-symmetry crystalline order as a result of photoinduced suppression of low-symmetry local lattice distortion. This distortion, which is a signature of nematic fluctuations, is corroborated by x-ray pair distribution function analysis and electron microscopy, and is present in a wide temperature range below and above the nematic phase transition.