Ultrafast Heat Transfer at the Nanoscale: Controlling Heat Anisotropy

Thermoplasmonics has benefited from increasing attention in recent years by exploiting the photothermal effects within plasmonic nanoparticles to generate nanoscale heat sources. Recently, it has been demonstrated that exciting gold nanoparticles with ultrashort light pulses could be used to achieve high-speed light management and nanoscale heat-sensitive chemical reaction control. In this work, we study non-uniform thermal energy transient distribution inside cross-shaped nanostructures with femtosecond transient spectroscopy coupled to a thermo-optical numerical model, free of fitting parameters. We show experimentally and numerically that the polarization of the excitation light can control the heat distribution in the nanostructures. We also demonstrate the necessity of considering nonthermal electron ballistic displacement in fast transient heat dynamics models.