Non-linear optics as probes of strongly correlated electron systems.

Jay Kikkawa, U. Penn

Pump-probe spectroscopy offers an opportunity to monitor the charge, spin and lattice degrees of freedom of non-equilibrium states. Applying this tool to the spin and charge systems of CMR manganites, I will explain how Kerr spectroscopy can be used to measure spin dynamics and compare our results with previous studies of spin dynamics based on charge dynamics. Signs of phase separation are reported and interpreted in terms of surface magnetic phases and/or microscopic phase separation. DC Kerr data at various probe energies are invoked to interpret the transient Kerr signal in terms of magnetization dynamics. Finally, I discuss the possibility of photo-induced transient magnetization in La_0.7Ca_0.3MnO_3 near T_c.