Ultrafast structural phase transition driven by photoinduced melting of charge and orbital order

Phys Rev Lett. 2009 Oct 9;103(15):155702. doi: 10.1103/PhysRevLett.103.155702. Epub 2009 Oct 9.


We use femtosecond x-ray diffraction to probe directly the structural dynamics of a charge ordered and orbitally ordered thin film of La0.42Ca0.58MnO3 initiated by an ultrafast optical pulse. At low excitation fluences we observe the displacive excitation of a coherent optical A(g) phonon. Under high excitation conditions we observe a complete phase transition within 1 ps via the disappearance of a superlattice reflection. The initial step of the phase transition occurs on a time scale significantly faster than the 200 fs time resolution of our experiment.