Symmetry Relation in Ultrafast Decay Processes of Single-Crystal Pt

Ultrafast electron dynamics plays a crucial role in understanding the properties of metals, particularly in the context of electron-phonon coupling (EPC). This study focuses on orientation-dependent ultrafast carrier dynamics in single-crystalline platinum films epitaxially grown on AlN-buffered sapphire substrates. Femtosecond time-resolved transient differential reflectance measurements reveal significant variations in the EPC constants across in-plane crystallographic directions, highlighting the influence of lattice symmetry. Theoretical analysis, based on group theory and Fermi's Golden Rule, shows that these ultrafast processes are affected by the symmetry of the platinum lattice, influencing the EPC dynamics. Unlike polycrystalline materials, single-crystalline platinum films exhibit distinct orientation-dependent behaviors, emphasizing the importance of crystallographic orientation in models. These findings provide new insights into ultrafast phenomena in metals and offer valuable perspectives for designing materials with tailored ultrafast properties for technological applications.