Ultrafast photoinduced reflectivity transients in $(Nd_{0.5}Sr_{0.5})MnO_3$

TL;DR

This study investigates the ultrafast photoinduced reflectivity in Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$ thin films, revealing complex temperature-dependent behaviors across different timescales and their relation to phase transitions and film inhomogeneity.

Contribution

It provides detailed analysis of ultrafast reflectivity transients in Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$, highlighting the different temperature sensitivities on sub-ps and ps timescales and their connection to phase transitions.

Findings

Sub-ps response weakly sensitive to metal-insulator transition.

Slower response correlates with phase transition.

Inhomogeneity affects ultrafast dynamics.

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.