Out-of-equilibrium dynamics of photoexcited spin-state concentration waves

Abstract

The spin crossover compound [Fe^IIH₂L^2-Me][PF₆]₂ presents a two-step phase transition. In the intermediate phase, a spin state concentration wave (SSCW) appears resulting from a symmetry breaking (cell doubling) associated with a long-range order of alternating high and low spin molecular states. By combining time-resolved optical and X-ray diffraction measurements on a single crystal, we study how such a system responds to femtosecond laser excitation and we follow in real time the erasing and rewriting of the SSCW.