Transient quantum isolation and critical behavior in the magnetization dynamics of half-metallic manganites

We combine time resolved pump-probe Magneto-Optical Kerr Effect and Photoelectron Spectroscopy experiments supported by theoretical analysis to determine the relaxation dynamics of delocalized electrons in half-metallic ferromagnetic manganite $La_{1-x}Sr_{x}MnO_{3}$. We observe that the half-metallic character of $La_{1-x}Sr_{x}MnO_{3}$ determines the timescale of both the electronic phase transition and the quenching of magnetization, revealing a quantum isolation of the spin system in double exchange ferromagnets extending up to hundreds of picoseconds. We demonstrate the use of time-resolved hard X-ray photoelectron spectroscopy (TR-HAXPES) as a unique tool to single out the evolution of strongly correlated electronic states across a second-order phase transition in a complex material.