Ultrafast photoinduced reflectivity transients in $(N{d}_{0.5}S{r}_{0.5})Mn{O}_3$

Abstract

The temperature dependence of ultrafast photoinduced reflectivity transients is reported in Nd${}_{0.5}$Sr${}_{0.5}$MnO${}_3$ thin film. The photoinduced reflectivity shows a complex response with very different temperature dependences on different timescales. The response on the sub-ps timescale appears to be only weakly sensitive to the 270K-metal-insulator phase transition. Below $\sim 160$ K the sub-ps response displays a two component behavior indicating inhomogeneity of the film resulting from the substrate induced strain. On the other hand, the slower response on the 10-100 ps timescale is sensitive only to the metal-insulator phase transition and is in agreement with some previously published results. The difference in the temperature dependences of the responses on nanosecond and $\mu$s timescales indicates that thermal equilibrium between the different degrees of fredom is established relatively slowly - on a nanosecond timescale.