Photo-induced Phase Transitions in Molecular Materials
Author: Wawrzyniec Kaszub
Publisher:
Published: 2012
Total Pages: 153
ISBN-13:
DOWNLOAD EBOOKThe main purpose of this Ph. D. thesis is to study the photo-induced transformations by a laser pulse in molecular materials. The results have been obtained thanks the use of pump-probe optical techniques. This required innovative experimental developments, including first attempts with a single shot technique. In the spincrosover family of molecular materials, in which light may induce the switching from a non magnetic to a magnetic state, for the first time we followed the transformation dynamics over ten decades in time scale, from 100 femtoseconds to a millisecond. It reveals that the process follows a complex pathway from molecular to material scale through a sequence of steps. A charge transfer organic compound, which exhibits an insulatior-to-metal phase transition, has also been investigated. A dynamics implying several coherent optical phonon modes has been clearly observed. The behaviour as a function of laser pulse intensity and temperature shows that the state photo-induced from the insulating phase differs from the metallic phase at thermal equilibrium. The newly developed single shot set-up proved able of recording changes upon an irreversible transformation, for instance inside a hysteresis regime. This set has been tested by observing photo-induced damages of a thin gold layer.